0000875045-22-000031 | 10-Q | XBRL Viewer

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Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2022	Oct. 24, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	0-19311
Entity Registrant Name	BIOGEN INC.
Entity Central Index Key	0000875045
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0112644
Entity Address, Address Line One	225 Binney Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	679-2000
Title of 12(b) Security	Common Stock, $0.0005 par value
Trading Symbol	BIIB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		144,001,404

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Total revenue	$ 2,508.5	$ 2,778.9	$ 7,629.4	$ 8,247.9
Cost and expenses:
Cost of sales, excluding amortization and impairment of acquired intangible assets	469.5	511.8	1,707.4	1,449.6
Research and development	549.2	702.4	1,629.5	1,801.7
Selling, general and administrative	563.3	654.1	1,770.8	1,886.4
Amortization and impairment of acquired intangible assets	56.5	111.0	190.9	813.2
Collaboration profit (loss) sharing	45.3	21.2	(42.6)	74.5
(Gain) loss on fair value remeasurement of contingent consideration	(2.1)	(15.6)	(13.7)	(49.1)
Acquired in-process research and development	0.0	0.0	0.0	18.0
Restructuring charges	15.4	0.0	124.1	0.0
Gain on sale of building	(503.7)	0.0	(503.7)	0.0
Other (income) expense, net	(56.0)	502.9	(221.3)	913.4
Total cost and expense	1,137.4	2,487.8	4,641.4	6,907.7
Income before income tax expense and equity in loss of investee, net of tax	1,371.1	291.1	2,988.0	1,340.2
Income tax (benefit) expense	236.2	(25.9)	578.5	(390.7)
Equity in (income) loss of investee, net of tax	0.0	(1.1)	(2.6)	(17.2)
Net income	1,134.9	318.1	2,412.1	1,748.1
Net income (loss) attributable to noncontrolling interests, net of tax	0.2	(11.1)	(84.4)	560.2
Net income attributable to Biogen Inc.	$ 1,134.7	$ 329.2	$ 2,496.5	$ 1,187.9
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 7.86	$ 2.22	$ 17.12	$ 7.93
Diluted earnings per share attributable to Biogen Inc.	$ 7.84	$ 2.22	$ 17.07	$ 7.90
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	144,400	148,000	145,800	149,900
Diluted earnings per share attributable to Biogen Inc.	144,800	148,600	146,200	150,300
Product, net
Total revenue	$ 1,962.1	$ 2,205.7	$ 6,083.3	$ 6,653.4
Revenue from anti-CD20 therapeutic programs
Total revenue	416.9	415.4	1,252.6	1,244.4
Other
Total revenue	$ 129.5	$ 157.8	$ 293.5	$ 350.1

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income attributable to Biogen Inc.	$ 1,134.7	$ 329.2	$ 2,496.5	$ 1,187.9
Other comprehensive income:
Unrealized gains (losses) on securities available for sale, net of tax	(1.0)	0.1	(19.0)	(1.4)
Unrealized gains (losses) on cash flow hedges, net of tax	5.9	66.2	79.0	205.0
Gains (losses) on net investment hedges, net of tax	0.0	15.1	(25.5)	35.2
Unrealized gains (losses) on pension benefit obligation, net of tax	1.5	1.5	4.2	3.9
Currency translation adjustment	(59.6)	(47.7)	(95.6)	(80.3)
Total other comprehensive income (loss), net of tax	(53.2)	35.2	(56.9)	162.4
Comprehensive income (loss) attributable to Biogen Inc.	1,081.5	364.4	2,439.6	1,350.3
Comprehensive income (loss) attributable to noncontrolling interests, net of tax	0.2	(11.1)	(84.4)	560.8
Comprehensive income (loss) attributable to noncontrolling interests, net of tax	$ 1,081.7	$ 353.3	$ 2,355.2	$ 1,911.1

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 3,675.6	$ 2,261.4
Marketable securities	1,235.5	1,541.1
Accounts receivable, net	1,568.8	1,549.4
Due from anti-CD20 therapeutic programs	415.4	412.3
Inventory	1,375.0	1,351.5
Other current assets	1,495.5	740.8
Total current assets	9,765.8	7,856.5
Marketable securities	860.3	892.0
Property, plant and equipment, net	3,266.4	3,416.4
Operating lease assets	424.5	375.4
Intangible assets, net	2,008.9	2,221.3
Goodwill	5,741.2	5,761.1
Deferred tax asset	1,174.5	1,415.1
Investments and other assets	1,612.6	1,939.5
Total assets	24,854.2	23,877.3
Current liabilities:
Current portion of notes payable	0.0	999.1
Taxes payable	237.3	174.7
Accounts payable	383.2	589.2
Accrued expense and other	3,305.9	2,535.2
Total current liabilities	3,926.4	4,298.2
Notes payable	6,279.2	6,274.0
Deferred tax liability	328.9	694.5
Long-term operating lease liabilities	354.8	330.4
Other long-term liabilities	1,198.1	1,320.5
Total liabilities	12,087.4	12,917.6
Commitments, contingencies and guarantees
Biogen Idec Inc. shareholders' equity
Preferred stock, par value $0.001 per share	0.0	0.0
Common stock, par value $0.0005 per share	0.1	0.1
Additional paid-in capital	0.0	68.2
Accumulated other comprehensive income (loss)	(163.6)	(106.7)
Retained earnings	15,916.1	13,911.7
Treasury stock, at cost	(2,977.1)	(2,977.1)
Total Biogen Inc. shareholders’ equity	12,775.5	10,896.2
Noncontrolling interests	(8.7)	63.5
Total equity	12,766.8	10,959.7
Total liabilities and equity	$ 24,854.2	$ 23,877.3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flow from operating activities:
Net income	$ 2,412.1	$ 1,748.1
Adjustments to reconcile net income to net cash flow from operating activities:
Depreciation and amortization	398.6	353.0
Impairment of intangible assets	0.0	629.3
Excess and obsolescence charges related to inventory	321.6	36.5
Acquired in-process research and development	0.0	18.0
Share-based compensation	186.9	179.8
Contingent consideration	(13.7)	(49.1)
Deferred income taxes	(139.8)	(750.1)
(Gain) loss on strategic investments	160.3	710.5
(Gain) loss on equity method investments	(2.6)	(17.2)
Gain on sale of equity interest in Samsung Bioepis	(1,505.4)	0.0
Gain on sale of building	(503.7)	0.0
Other	147.8	164.5
Changes in operating assets and liabilities, net:
Accounts receivable	(109.5)	157.8
Due from anti-CD20 therapeutic programs	(3.0)	13.5
Inventory	(338.3)	(322.6)
Accrued expense and other current liabilities	632.3	(243.3)
Income tax assets and liabilities	(100.2)	260.5
Other changes in operating assets and liabilities, net	15.9	(87.6)
Net cash flow provided by (used in) operating activities	1,559.3	2,801.6
Cash flows from investing activities:
Purchases of property, plant and equipment	(153.9)	(206.5)
Proceeds from sales and maturities of marketable securities	3,104.7	2,028.1
Purchases of marketable securities	(2,805.9)	(2,372.6)
Proceeds from sale of equity interest in Samsung Bioepis	(990.3)	0.0
Proceeds from sale of building	582.6	0.0
Proceeds from divestiture of Hillerød, Denmark manufacturing operations	0.0	28.1
Acquired in-process research and development	0.0	(18.0)
Acquisitions of intangible assets	(1.9)	(1.9)
Proceeds from sales of strategic investments	0.0	91.2
Other	1.8	0.6
Net cash flow provided by (used in) investing activities	1,717.7	(451.0)
Cash flows from financing activities:
Purchases of treasury stock	(750.0)	(1,800.0)
Payments related to issuance of stock for share-based compensation arrangements, net	(5.8)	(8.3)
Repayment of borrowings and premiums paid	(1,002.2)	(170.0)
Net (distribution) contribution to noncontrolling interest	12.2	(94.8)
Other	5.9	(22.9)
Net cash flow provided by (used in) financing activities	(1,739.9)	(2,096.0)
Net increase (decrease) in cash and cash equivalents	1,537.1	254.6
Effect of exchange rate changes on cash and cash equivalents	(122.9)	(44.0)
Cash and cash equivalents, beginning of the period	2,261.4	1,331.2
Cash and cash equivalents, end of the period	$ 3,675.6	$ 1,541.8

Condensed Consolidated Statement of Equity Statement - USD ($) shares in Millions, $ in Millions	Total	Preferred stock	Common stock	Additional paid-in capital	Accumulated Other Comprehensive Income	Retained earnings	Treasury stock	Parent	Noncontrolling interest	2020 Share Repurchase Program	2020 Share Repurchase Program Common stock	2020 Share Repurchase Program Additional paid-in capital	2020 Share Repurchase Program Retained earnings	2020 Share Repurchase Program Treasury stock	2020 Share Repurchase Program Parent
Beginning balance, shares at Dec. 31, 2020		0.0	176.2				23.8
Beginning balance at Dec. 31, 2020	$ 10,686.1	$ 0.0	$ 0.1	$ 0.0	$ (299.0)	$ 13,976.3	$ (2,977.1)	$ 10,700.3	$ (14.2)
Net income	1,748.1					1,187.9		1,187.9	560.2
Other comprehensive income (loss), net of tax	163.0				162.4			162.4	0.6
Capital contribution from noncontrolling interest	5.2								5.2
Distribution to noncontrolling interest	(100.0)								(100.0)
Repurchase of common stock, at cost, shares										(6.0)				(6.0)
Repurchase of common stock, at cost										$ (1,800.0)				$ (1,800.0)	$ (1,800.0)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares											(6.0)			(6.0)
Retirement of common stock pursuant to Share Repurchase Progams, at cost												$ (231.9)	$ (1,568.1)	$ 1,800.0
Issuance of common stock under stock option and stock purchase plans, shares			0.2
Issuance of common stock under stock option and stock purchase plans	44.3			44.3				44.3
Issuance of common stock under award plan, shares			0.3
Issuance of common stock under stock award plan	(52.6)					(52.6)		(52.6)
Compensation related to share-based payments	186.1			186.1				186.1
Other	1.5			1.5				1.5
Ending balance at Sep. 30, 2021	10,881.7	$ 0.0	$ 0.1	0.0	(136.6)	13,543.5	$ (2,977.1)	10,429.9	451.8
Ending balance, shares at Sep. 30, 2021		0.0	170.7				23.8
Beginning balance, shares at Jun. 30, 2021		0.0	172.9				23.8
Beginning balance at Jun. 30, 2021	11,214.8	$ 0.0	$ 0.1	0.0	(171.8)	13,900.7	$ (2,977.1)	10,751.9	462.9
Net income	318.1					329.2		329.2	(11.1)
Other comprehensive income (loss), net of tax	35.2				35.2			35.2	0.0
Repurchase of common stock, at cost, shares										(2.2)				(2.2)
Repurchase of common stock, at cost										$ (750.0)				$ (750.0)	(750.0)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares											(2.2)			(2.2)
Retirement of common stock pursuant to Share Repurchase Progams, at cost												(68.6)	(681.4)	$ 750.0
Issuance of common stock under stock option and stock purchase plans, shares			0.0
Issuance of common stock under stock option and stock purchase plans	11.0			11.0				11.0
Issuance of common stock under award plan, shares			0.0
Issuance of common stock under stock award plan	(5.0)					(5.0)		(5.0)
Compensation related to share-based payments	57.6			57.6				57.6
Ending balance at Sep. 30, 2021	10,881.7	$ 0.0	$ 0.1	0.0	(136.6)	13,543.5	$ (2,977.1)	10,429.9	451.8
Ending balance, shares at Sep. 30, 2021		0.0	170.7				23.8
Beginning balance, shares at Dec. 31, 2021		0.0	170.8				23.8
Beginning balance at Dec. 31, 2021	10,959.7	$ 0.0	$ 0.1	68.2	(106.7)	13,911.7	$ (2,977.1)	10,896.2	63.5
Net income	2,412.1					2,496.5		2,496.5	(84.4)
Other comprehensive income (loss), net of tax	(56.9)				(56.9)			(56.9)
Capital contribution from noncontrolling interest	12.2								12.2
Repurchase of common stock, at cost, shares														(3.6)
Repurchase of common stock, at cost										$ (750.0)				$ (750.0)	(750.0)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares										(3.6)	(3.6)			(3.6)
Retirement of common stock pursuant to Share Repurchase Progams, at cost										$ (750.0)		(257.9)	(492.1)	$ 750.0
Issuance of common stock under stock option and stock purchase plans, shares			0.2
Issuance of common stock under stock option and stock purchase plans	37.5			37.5				37.5
Issuance of common stock under award plan, shares			0.4
Issuance of common stock under stock award plan	(43.2)			(43.2)				(43.2)
Compensation related to share-based payments	194.1			194.1				194.1
Other	1.3			1.3				1.3
Ending balance at Sep. 30, 2022	12,766.8	$ 0.0	$ 0.1	0.0	(163.6)	15,916.1	$ (2,977.1)	12,775.5	(8.7)
Ending balance, shares at Sep. 30, 2022		0.0	167.8				23.8
Beginning balance, shares at Jun. 30, 2022		0.0	169.0				23.8
Beginning balance at Jun. 30, 2022	11,863.4	$ 0.0	$ 0.1	0.0	(110.4)	14,959.9	$ (2,977.1)	11,872.5	(9.1)
Net income	1,134.9					1,134.7		1,134.7	0.2
Other comprehensive income (loss), net of tax	(53.2)				(53.2)			(53.2)
Capital contribution from noncontrolling interest	0.2								0.2
Repurchase of common stock, at cost, shares														(1.2)
Repurchase of common stock, at cost										$ (250.0)				$ (250.0)	$ (250.0)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares										(1.2)	(1.2)			(1.2)
Retirement of common stock pursuant to Share Repurchase Progams, at cost	0.0									$ (250.0)		$ (71.5)	$ (178.5)	$ 250.0
Issuance of common stock under stock option and stock purchase plans, shares			0.0
Issuance of common stock under stock option and stock purchase plans	8.6			8.6				8.6
Issuance of common stock under award plan, shares			0.0
Issuance of common stock under stock award plan	(2.8)			(2.8)				(2.8)
Compensation related to share-based payments	65.7			65.7				65.7
Other	0.0			0.0				0.0
Ending balance at Sep. 30, 2022	$ 12,766.8	$ 0.0	$ 0.1	$ 0.0	$ (163.6)	$ 15,916.1	$ (2,977.1)	$ 12,775.5	$ (8.7)
Ending balance, shares at Sep. 30, 2022		0.0	167.8				23.8

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2022
Accounting Policies [Abstract]
Summary of significant accounting policies	References in these notes to "Biogen," the "company," "we," "us" and "our" refer to Biogen Inc. and its consolidated subsidiaries. Business Overview Biogen is a global biopharmaceutical company focused on discovering, developing and delivering worldwide innovative therapies for people living with serious neurological and neurodegenerative diseases as well as related therapeutic adjacencies. We have a leading portfolio of medicines to treat multiple sclerosis (MS), have introduced the first approved treatment for spinal muscular atrophy (SMA) and developed the first and only approved treatment to address a defining pathology of Alzheimer's disease. We also commercialize biosimilars of advanced biologics and focus on advancing our pipeline in neuroscience and specialized immunology. Lastly, we are focused on accelerating our efforts in digital health to support our commercial and pipeline programs while also creating opportunities for potential digital therapeutics. We support our drug discovery and development efforts through the commitment of significant resources to discovery, research and development programs and business development opportunities. Our marketed products include TECFIDERA, VUMERITY, AVONEX, PLEGRIDY, TYSABRI and FAMPYRA for the treatment of MS; SPINRAZA for the treatment of SMA; ADUHELM for the treatment of Alzheimer's disease; and FUMADERM for the treatment of severe plaque psoriasis. We have certain business and financial rights with respect to RITUXAN for the treatment of non-Hodgkin's lymphoma, chronic lymphocytic leukemia (CLL) and other conditions; RITUXAN HYCELA for the treatment of non-Hodgkin's lymphoma and CLL; GAZYVA for the treatment of CLL and follicular lymphoma; OCREVUS for the treatment of primary progressive MS (PPMS) and relapsing MS (RMS); and other potential anti-CD20 therapies, including mosunetuzumab, pursuant to our collaboration arrangements with Genentech, Inc. (Genentech), a wholly-owned member of the Roche Group. For additional information on our collaboration arrangements with Genentech, please read Note 18, Collaborative and Other Relationships, to our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2021 (2021 Form 10-K). Our innovative drug development and commercialization activities are complemented by our biosimilar business that expands access to medicines and reduces the cost burden for healthcare systems. Through our collaboration with Samsung Bioepis Co., Ltd. (Samsung Bioepis) we market and sell BENEPALI, an etanercept biosimilar referencing ENBREL, IMRALDI, an adalimumab biosimilar referencing HUMIRA, and FLIXABI, an infliximab biosimilar referencing REMICADE, in certain countries in Europe, as well as BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS. For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 18, Collaborative and Other Relationships, to these unaudited condensed consolidated financial statements (condensed consolidated financial statements). Basis of Presentation In the opinion of management, our condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair statement of our financial statements for interim periods in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The information included in this quarterly report on Form 10-Q should be read in conjunction with our audited consolidated financial statements and the accompanying notes included in our 2021 Form 10-K. Our accounting policies are described in the Notes to Consolidated Financial Statements in our 2021 Form 10-K and updated, as necessary, in this report. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP. The results of operations for the three and nine months ended September 30, 2022, are not necessarily indicative of the operating results for the full year or for any other subsequent interim period. We operate as one operating segment, focused on discovering, developing and delivering worldwide innovative therapies for people living with serious neurological and neurodegenerative diseases as well as related therapeutic adjacencies. Consolidation Our condensed consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and those of certain variable interest entities where we are the primary beneficiary. For consolidated entities where we own or are exposed to less than 100.0% of the economics, we record net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. Intercompany balances and transactions are eliminated in consolidation. In determining whether we are the primary beneficiary of a variable interest entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. We continuously assess whether we are the primary beneficiary of a variable interest entity as changes to existing relationships or future transactions may result in us consolidating or deconsolidating one or more of our collaborators or partners. Use of Estimates The preparation of our condensed consolidated financial statements requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, equity, revenue and expense and related disclosure of contingent assets and liabilities. On an ongoing basis we evaluate our estimates, judgments and assumptions. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets, liabilities and equity and the amount of revenue and expense. Actual results may differ from these estimates. The length of time and full extent to which the COVID-19 pandemic directly or indirectly impacts our business, results of operations and financial condition, including sales, expense, reserves and allowances, the supply chain, manufacturing, clinical trials, research and development costs and employee-related costs, depends on future developments that are highly uncertain, subject to change and are difficult to predict, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat COVID-19 as well as the economic impact on local, regional, national and international customers and markets. Additionally, the ongoing geopolitical tensions related to the conflict in Ukraine, and the related sanctions and other penalties imposed, are creating substantial uncertainty in the global economy. The extent and duration of the conflict, sanctions and resulting market disruptions are highly unpredictable. We have made estimates of the impact of the COVID-19 pandemic and the ongoing geopolitical conflict within our condensed consolidated financial statements and there may be changes to those estimates in future periods. New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed below, we do not believe that the adoption of recently issued standards have had or may have a material impact on our condensed consolidated financial statements or disclosures. Fair Value Measurements In June 2022 the FASB issued Accounting Standards Update (ASU) No. 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. This standard clarifies that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. This standard becomes effective for us on January 1, 2024. We elected to early adopt this standard on a prospective basis during the third quarter of 2022.

Restructuring, Business Transformation and Other Cost Saving Initiatives

9 Months Ended

Sep. 30, 2022

Restructuring and Related Activities [Abstract]

Restructuring, Business Transformation and Other Cost Saving Initiatives

RESTRUCTURING

2022 Cost Saving Initiatives

In December 2021 and May 2022 we announced our plans to implement a series of cost-reduction measures during 2022. These savings are being achieved through a number of initiatives, including reductions to our workforce, the substantial elimination of our commercial ADUHELM infrastructure, the consolidation of certain real estate locations and operating efficiencies across our selling, general and administrative and research and development functions.

Under these initiatives, we expect to incur restructuring charges ranging from approximately $130.0 million to $150.0 million. These amounts are primarily related to severance and are expected to be substantially incurred and paid by the end of 2022.

For the three and nine months ended September 30, 2022, we recognized approximately $15.4 million and $124.1 million, respectively, of net pre-tax restructuring charges related to our 2022 cost saving initiatives, of which approximately $21.6 million and $110.2 million, respectively, consisted of employee severance costs. These costs were recorded in restructuring charges in our condensed consolidated statements of income. Our restructuring reserve is included in accrued expense and other in our condensed consolidated balance sheets. In September 2022 we entered into an agreement to partially terminate a portion of our lease located at 300 Binney Street, Cambridge, MA (300 Binney Street), as well as to reduce the lease term for the majority of the remaining space. This resulted in a gain of approximately $5.3 million, which was recorded within restructuring charges in our condensed consolidated statements of income for the three and nine months ended September 30, 2022. For additional information on our 300 Binney Street lease modification, please read Note 11, Leases, to these condensed consolidated financial statements.

Following an evaluation of our current capacity needs, in March 2022 we ceased using a patient services office space in Durham, North Carolina. Our decision to cease use of the facility resulted in the immediate expense of certain leasehold improvements and other assets at this facility. As a result, for the nine months ended September 30, 2022, we recognized approximately $10.4 million of accelerated depreciation expense, which was recorded in restructuring charges in our condensed consolidated statements of income. In May 2022 we entered into a lease assignment agreement whereby we assigned our remaining lease obligations to an external third party. As a result of the lease assignment, we derecognized the related operating lease obligation and right-of-use asset during the second quarter of 2022.

For the nine months ended September 30, 2022, we recognized other restructuring costs of approximately $8.8 million, which were recorded in restructuring charges in our condensed consolidated statements of income. Other restructuring costs include items such as facility closure costs, employee non-severance expense, asset write-offs and other costs.

The following table summarizes the charges and spending related to our 2022 workforce reductions for the three and nine months ended September 30, 2022:


(In millions)	Total
Restructuring reserve as of December 31, 2021	$	—
Expense	27.7
Payment	(6.2)

Restructuring reserve as of March 31, 2022	21.5
Expense	60.9
Payment	(29.7)
Foreign currency and other adjustments	(0.5)
Restructuring reserve as of June 30, 2022	52.2
Expense	21.6
Payment	(32.3)
Foreign currency and other adjustments	(1.3)
Restructuring reserve as of September 30, 2022	$	40.2

Revenues

9 Months Ended

Sep. 30, 2022

Revenue from Contract with Customer [Abstract]

Revenues

Product Revenue

Revenue by product is summarized as follows:


	For the Three Months Ended September 30,
	2022						2021
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
TECFIDERA	$	92.5	$	246.5	$	339.0	$	179.2	$	319.4	$	498.6
VUMERITY(1)	127.9		9.9		137.8		120.7		0.2		120.9
Total Fumarate	220.4		256.4		476.8		299.9		319.6		619.5
AVONEX	174.8		80.3		255.1		213.2		88.1		301.3
PLEGRIDY	39.7		41.2		80.9		39.2		47.0		86.2
Total Interferon	214.5		121.5		336.0		252.4		135.1		387.5
TYSABRI	273.0		232.5		505.5		281.1		241.7		522.8
FAMPYRA	—		22.0		22.0		—		26.2		26.2
Subtotal: MS	707.9		632.4		1,340.3		833.4		722.6		1,556.0

Spinal Muscular Atrophy:
SPINRAZA	140.2		290.9		431.1		139.8		304.3		444.1

Biosimilars:
BENEPALI	—		110.2		110.2		—		120.8		120.8
IMRALDI	—		57.7		57.7		—		57.4		57.4
FLIXABI	—		19.0		19.0		—		24.6		24.6
BYOOVIZ(2)	0.7		—		0.7		—		—		—
Subtotal: Biosimilars	0.7		186.9		187.6		—		202.8		202.8

Other:
FUMADERM	—		1.5		1.5		—		2.5		2.5
ADUHELM	1.6		—		1.6		0.3		—		0.3
Total product revenue	$	850.4	$	1,111.7	$	1,962.1	$	973.5	$	1,232.2	$	2,205.7

(1) VUMERITY became commercially available in the European Union (E.U.) during the fourth quarter of 2021.

(2) BYOOVIZ launched in the United States (U.S.) in June 2022 and became commercially available during the third quarter of 2022.


	For the Nine Months Ended September 30,
	2022						2021
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
TECFIDERA	$	330.3	$	816.5	$	1,146.8	$	520.1	$	945.3	$	1,465.4
VUMERITY(1)	383.0		19.6		402.6		285.0		0.5		285.5
Total Fumarate	713.3		836.1		1,549.4		805.1		945.8		1,750.9
AVONEX	493.8		249.6		743.4		636.4		286.9		923.3
PLEGRIDY	114.2		138.2		252.4		115.2		149.9		265.1
Total Interferon	608.0		387.8		995.8		751.6		436.8		1,188.4
TYSABRI	849.4		693.1		1,542.5		854.2		696.2		1,550.4
FAMPYRA	—		73.7		73.7		—		78.8		78.8
Subtotal: MS	2,170.7		1,990.7		4,161.4		2,410.9		2,157.6		4,568.5

Spinal Muscular Atrophy:
SPINRAZA	443.3		891.4		1,334.7		437.8		1,026.6		1,464.4

Biosimilars:
BENEPALI	—		340.7		340.7		—		363.9		363.9
IMRALDI	—		172.4		172.4		—		170.9		170.9
FLIXABI	—		62.0		62.0		—		75.4		75.4
BYOOVIZ(2)	1.2		—		1.2		—		—		—
Subtotal: Biosimilars	1.2		575.1		576.3		—		610.2		610.2

Other:
FUMADERM	—		6.4		6.4		—		8.3		8.3
ADUHELM	4.5		—		4.5		2.0		—		2.0
Total product revenue	$	2,619.7	$	3,463.6	$	6,083.3	$	2,850.7	$	3,802.7	$	6,653.4

(1) VUMERITY became commercially available in the E.U. during the fourth quarter of 2021.

(2) BYOOVIZ launched in the U.S. in June 2022 and became commercially available during the third quarter of 2022.

We recognized revenue from two wholesalers accounting for 26.9% and 10.5% of gross product revenue for the three months ended September 30, 2022, and 26.8% and 10.7% of gross product revenue for the nine months ended September 30, 2022.

We recognized revenue from two wholesalers accounting for 26.9% and 10.8% of gross product revenue for the three months ended September 30, 2021, and 29.1% and 10.0% of gross product revenue for the nine months ended September 30, 2021.

An analysis of the change in reserves for discounts and allowances is summarized as follows:


(In millions)	Discounts		Contractual Adjustments		Returns		Total
Balance, December 31, 2021	$	137.7	$	759.6	$	38.0	$	935.3
Current provisions relating to sales in current year	499.3		1,993.6		8.5		2,501.4
Adjustments relating to prior years	(2.5)		(18.4)		(7.7)		(28.6)
Payments/credits relating to sales in current year	(379.6)		(1,442.0)		—		(1,821.6)
Payments/credits relating to sales in prior years	(124.5)		(463.7)		(14.4)		(602.6)
Balance, September 30, 2022	$	130.4	$	829.1	$	24.4	$	983.9

The total reserves above, which are included in our condensed consolidated balance sheets, are summarized as follows:


(In millions)	As of September 30, 2022		As of December 31, 2021
Reduction of accounts receivable	$	129.4	$	133.2
Component of accrued expense and other	854.5		802.1
Total revenue-related reserves	$	983.9	$	935.3

Revenue from Anti-CD20 Therapeutic Programs

Revenue from anti-CD20 therapeutic programs is summarized in the table below. For the purposes of this footnote, we refer to RITUXAN and RITUXAN HYCELA collectively as RITUXAN.


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Biogen’s share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	$	131.1	$	145.8	$	414.2	$	498.7
OCREVUS and other revenue from anti-CD20 therapeutic programs	285.8		269.6		838.4		745.7
Total revenue from anti-CD20 therapeutic programs	$	416.9	$	415.4	$	1,252.6	$	1,244.4

For additional information on our collaboration arrangements with Genentech, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

Other Revenue

Other revenue is summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Revenue from collaborative and other relationships:
Revenue earned under our technical development agreement, manufacturing services agreements and royalty revenue on biosimilar products with Samsung Bioepis	$	6.5	$	6.3	$	20.9	$	15.7

Other royalty and corporate revenue:
Royalty	8.8		7.7		29.7		20.3
Other corporate	114.2		143.8		242.9		314.1
Total other revenue	$	129.5	$	157.8	$	293.5	$	350.1

We receive royalties from net sales on products related to patents that we have out-licensed and we record other corporate revenue primarily from amounts earned under contract manufacturing agreements.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Inventory

9 Months Ended

Sep. 30, 2022

Inventory Disclosure [Abstract]

Inventory

The components of inventory are summarized as follows:


(In millions)	As of September 30, 2022		As of December 31, 2021
Raw materials	$	394.2	$	349.6
Work in process(1)	771.0		814.0
Finished goods	209.8		187.9
Total inventory	$	1,375.0	$	1,351.5

(1) Work in process inventory as of September 30, 2022, includes approximately $118.0 million related to lecanemab.

In April 2022 the Centers for Medicare and Medicaid Services (CMS) released the final National Coverage Decision (NCD) for the class of anti-amyloid treatments in Alzheimer’s disease, including ADUHELM. The final NCD confirmed coverage with evidence development, in which patients with Medicare can only access treatment if they are part of an approved clinical trial. We expect that this decision will reduce future demand for ADUHELM to a minimal level. During the first quarter of 2022 we wrote-off approximately $275.0 million of inventory related to

ADUHELM, as a result of this CMS decision, which was recognized in cost of sales within our condensed consolidated statements of income for the nine months ended September 30, 2022. We have recognized approximately $136.0 million related to Eisai's 45.0% share of these charges in collaboration profit (loss) sharing within our condensed consolidated statements of income for the nine months ended September 30, 2022.

During the fourth quarter of 2021 we wrote-off approximately $120.0 million of inventory in excess of forecasted demand related to ADUHELM, which was recognized in cost of sales within our condensed consolidated statements of income for the year ended December 31, 2021. We have recognized approximately $59.0 million related to Eisai's 45.0% share of these charges in collaboration profit (loss) sharing within our condensed consolidated statements of income for the year ended December 31, 2021.

As of September 30, 2022, the carrying value of our ADUHELM inventory was de minimis. As of December 31, 2021, we had approximately $223.0 million of ADUHELM inventory. For additional information please read Note 18, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Intangible Assets and Goodwill

9 Months Ended

Sep. 30, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets and Goodwill

Intangible Assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments are summarized as follows:


		As of September 30, 2022						As of December 31, 2021
(In millions)	Estimated Life	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Completed technology	4-28 years	$	7,415.0	$	(5,579.4)	$	1,835.6	$	7,413.1	$	(5,388.5)	$	2,024.6
In-process research and development	Indefinite until commercialization	109.3		—		109.3		132.7		—		132.7
Trademarks and trade names	Indefinite	64.0		—		64.0		64.0		—		64.0
Total intangible assets		$	7,588.3	$	(5,579.4)	$	2,008.9	$	7,609.8	$	(5,388.5)	$	2,221.3

Amortization and Impairments

For the three and nine months ended September 30, 2022, amortization and impairment of acquired intangible assets totaled $56.5 million and $190.9 million, respectively, compared to $111.0 million and $813.2 million, respectively, in the prior year comparative periods. For the three and nine months ended September 30, 2022, we had no impairment charges.

For the three and nine months ended September 30, 2021, amortization and impairment of acquired intangible assets reflects impairment charges of $15.0 million and $365.0 million, respectively, related to BIIB111 (timrepigene emparvovec) for the potential treatment of choroideremia and impairment charges of $28.4 million and $220.0 million, respectively, related to BIIB112 (cotoretigene toliparvovec) for the potential treatment of X-linked retinitis pigmentosa.

For the nine months ended September 30, 2021, amortization and impairment of acquired intangible assets also reflects a $44.3 million impairment charge related to vixotrigine (BIIB074) for the potential treatment of trigeminal neuralgia (TGN).

Completed Technology

Completed technology primarily relates to our acquisition of all remaining rights to TYSABRI as well as other amounts related to our other marketed products and programs acquired through business combinations.

IPR&D Related to Business Combinations

In-process research and development (IPR&D) represents the fair value assigned to research and development assets that we acquired as part of a business combination and had not yet reached technological feasibility at the date of acquisition. Included in IPR&D balances are adjustments related to foreign currency exchange rate fluctuations. We review amounts capitalized as acquired IPR&D for impairment annually, as of October 31, and whenever events or changes in circumstances indicate to us that the carrying value of the assets might not be recoverable. The carrying value associated with our IPR&D assets as of September 30, 2022, relates to the IPR&D programs we acquired in connection with our acquisition of Convergence Pharmaceuticals Holdings Ltd. (Convergence).

Vixotrigine

In the periods since we acquired vixotrigine, there have been numerous delays in the initiation of Phase 3 studies for the potential treatment of TGN and for the potential treatment of diabetic painful neuropathy (DPN), another form of neuropathic pain. We have engaged with the U.S. Food and Drug Administration (FDA) regarding the design of the Phase 3 studies of vixotrigine for the potential treatment of TGN and DPN and are now performing an additional clinical trial of vixotrigine, which is expected to be completed by the end of 2022.

The performance of this additional clinical trial has delayed the initiation of the Phase 3 studies of vixotrigine for the potential treatment of TGN, and, as a result, we recognized an impairment charge of $44.3 million related to vixotrigine for the potential treatment of TGN during the first quarter of 2021.

As of September 30, 2022, the carrying value associated with the remaining vixotrigine IPR&D intangible asset for DPN was $109.3 million and the fair value of this asset was not significantly in excess of its carrying value. We will reassess the carrying value of this program upon conclusion of the ongoing clinical trial, or sooner if there is a reevaluation event, and may record an impairment charge related to this asset.

BIIB111 and BIIB112

During the second quarter of 2021 we announced that our Phase 3 STAR study of BIIB111 and our Phase 2/3 XIRIUS study of BIIB112 did not meet their primary endpoints. In the third quarter of 2021 we suspended further development on these programs based on the decision by management as part of its strategic review process. For the three and nine months ended September 30, 2021, we recognized impairment charges of $15.0 million and $365.0 million, respectively, related to BIIB111, and impairment charges of $28.4 million and $220.0 million, respectively, related to BIIB112, reducing the remaining book values of these IPR&D intangible assets to zero.

In addition, as a result of our decision to suspend further development of BIIB111 and BIIB112, we recorded charges of approximately $39.1 million during the third quarter of 2021 related to our manufacturing arrangements and other costs that we expect to incur as a result of suspending these programs.

Estimated Future Amortization of Intangible Assets

The estimated future amortization of finite-lived intangible assets for the next five years is expected to be as follows:


(In millions)	As of September 30, 2022
2022 (remaining three months)	$	55.0
2023	215.0
2024	195.0
2025	190.0
2026	175.0
2027	165.0

Goodwill

The following table provides a roll forward of the changes in our goodwill balance:


(In millions)	As of September 30, 2022
Goodwill, December 31, 2021	$	5,761.1

Other	(19.9)
Goodwill, September 30, 2022	$	5,741.2

As of September 30, 2022, we had no accumulated impairment losses related to goodwill. Other includes adjustments related to foreign currency exchange rate fluctuations.

Fair Value Measurements

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Fair Value Measurements

The tables below present information about our assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques we utilized to determine such fair value:


	Fair Value Measurements on a Recurring Basis
	As of September 30, 2022
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	3,191.8	$	—	$	3,191.8	$	—
Marketable debt securities:
Corporate debt securities	1,219.1		—		1,219.1		—
Government securities	702.0		—		702.0		—
Mortgage and other asset backed securities	174.7		—		174.7		—
Marketable equity securities	896.0		896.0		—		—
Other current assets:
Receivable from Samsung BioLogics(1)	790.8		—		—		790.8
Other assets:
Derivative contracts	195.9		—		195.9		—
Plan assets for deferred compensation	32.2		—		32.2		—
Receivable from Samsung BioLogics(1)	402.8		—		—		402.8
Total	$	7,605.3	$	896.0	$	5,515.7	$	1,193.6
Liabilities:
Derivative contracts	$	22.8	$	—	$	22.8	$	—
Contingent consideration obligations	195.4		—		—		195.4
Total	$	218.2	$	—	$	22.8	$	195.4

(1) Represents the fair value of the current and non-current payments due from Samsung BioLogics as a result of the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics during the second quarter of 2022, for which we elected the fair value option. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.


	Fair Value Measurements on a Recurring Basis
	As of December 31, 2021
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,632.2	$	—	$	1,632.2	$	—
Marketable debt securities:
Corporate debt securities	1,108.2		—		1,108.2		—
Government securities	1,192.7		—		1,192.7		—
Mortgage and other asset backed securities	132.2		—		132.2		—
Marketable equity securities	1,048.5		181.7		866.8		—
Derivative contracts	80.9		—		80.9		—
Plan assets for deferred compensation	33.4		—		33.4		—
Total	$	5,228.1	$	181.7	$	5,046.4	$	—
Liabilities:
Derivative contracts	$	10.8	$	—	$	10.8	$	—
Contingent consideration obligations	209.1		—		—		209.1
Total	$	219.9	$	—	$	10.8	$	209.1

The fair value of Level 2 instruments classified as cash equivalents and marketable debt securities was determined through third-party pricing services. As of September 30, 2022, we elected to early adopt ASU 2022-03 on a prospective basis, which resulted in removing the impact of contractual sale restrictions from the fair value measurement of our remaining Sage common stock subject to certain holding period restrictions. As of September 30, 2022, our entire investment in the common stock of Sage was classified as a Level 1 measurement. Prior to the adoption of this standard, the fair value of Level 2 instruments classified as marketable equity securities represented a portion of our investment in the common stock of Sage and was valued using an option pricing valuation model. The initial holding period restriction for a portion of our investment in the common stock of Sage expired during the second quarter of 2022 with the remaining holding period restriction set to expire in the fourth quarter of 2022.

Our investments in the common stock of Sangamo Therapeutics, Inc. (Sangamo) and Denali Therapeutics Inc. (Denali) had holding period restrictions that expired during 2022. As of September 30, 2022, the fair values of our investments in Sangamo and Denali common stock were classified as Level 1 measurements. Prior to the expiration of these holding period restrictions the investments were classified as Level 2 measurements.

For additional information on our investments in Sangamo, Denali and Sage common stock, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

There have been no material impairments of our assets measured and carried at fair value as of September 30, 2022 and December 31, 2021. There have been no significant changes to our valuation techniques as of September 30, 2022 and December 31, 2021.

For a description of our validation procedures related to prices provided by third-party pricing services and our option pricing valuation model, please read Note 1, Summary of Significant Accounting Policies - Fair Value Measurements, to our consolidated financial statements included in our 2021 Form 10-K.

Level 3 Assets and Liabilities Held at Fair Value

The following table presents quantitative information, as of the dates indicated, about the valuation techniques and significant unobservable inputs used in the valuation of our level 3 financial assets and liabilities measured at fair value on a recurring basis:

Quantitative Information about Level 3 Fair Value Measurements

Fair Value

Weighted Average

(In millions)

September 30, 2022

December 31, 2021

Valuation Technique

Significant
Unobservable Input(s)

Range

September 30, 2022

December 31, 2021

Liabilities:

Contingent consideration obligations

195.4

209.1

Discounted cash flow

Discount rate

4.50%

4.50

1.30

Expected timing of achievement of development milestones

2023 to 2028

—

The weighted average discount rates were calculated based on the relative fair value of our contingent consideration obligations. In addition, we apply various probabilities of technological and regulatory success to the valuation models to estimate the fair values of our contingent consideration obligations, which ranged from 10.9% to certain probability as of September 30, 2022 and December 31, 2021.

There were no transfers of assets or liabilities into or out of Level 3 as of September 30, 2022 and December 31, 2021.

Contingent Consideration Obligations

In connection with our acquisitions of Convergence and Biogen International Neuroscience GmbH, we agreed to make additional payments based upon the achievement of certain milestone events. The following table provides a roll forward of the fair values of our contingent consideration obligations, which are classified as Level 3 measurements:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Fair value, beginning of period	$	197.5	$	226.3	$	209.1	$	259.8
Changes in fair value	(2.1)		(15.6)		(13.7)		(49.1)

Fair value, end of period	$	195.4	$	210.7	$	195.4	$	210.7

As of September 30, 2022 and December 31, 2021, approximately $195.4 million and $209.1 million, respectively, of the fair value of our total contingent consideration obligations was reflected as a component of other long-term liabilities in our condensed consolidated balance sheets with any remaining balances reflected as a component of accrued expense and other. Changes in the fair values of our contingent consideration obligations are recorded in (gain) loss on fair value remeasurement of contingent consideration in our condensed consolidated statements of income.

For the three and nine months ended September 30, 2022, the changes in the fair value of our contingent consideration obligations were primarily due to increases in the discount rates used to revalue these obligations and delays in the expected timing of the achievement of certain remaining developmental milestones related to our vixotrigine programs.

For the three and nine months ended September 30, 2021, the changes in the fair value of our contingent consideration obligations were primarily due to reductions in the probability of technical and regulatory success and delays in the expected timing of the achievement of certain remaining developmental milestones related to our vixotrigine programs.

Financial Instruments Not Carried at Fair Value

Other Financial Instruments

Due to the short-term nature of certain financial instruments, the carrying value reflected in our condensed consolidated balance sheets for current accounts receivable, due from anti-CD20 therapeutic programs, other current assets, accounts payable and accrued expense and other, approximates fair value.

Debt Instruments

The fair and carrying values of our debt instruments, which are Level 2 liabilities, are summarized as follows:


	As of September 30, 2022				As of December 31, 2021
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value

3.625% Senior Notes due September 15, 2022(1)	$	—	$	—	$	1,020.0	$	999.1
4.050% Senior Notes due September 15, 2025	1,697.8		1,744.3		1,895.2		1,742.9
2.250% Senior Notes due May 1, 2030	1,183.0		1,492.7		1,475.9		1,492.0
5.200% Senior Notes due September 15, 2045	997.2		1,100.2		1,463.0		1,099.9
3.150% Senior Notes due May 1, 2050	965.6		1,473.6		1,457.7		1,473.2
3.250% Senior Notes due February 15, 2051	452.8		468.4		692.9		466.0
Total	$	5,296.4	$	6,279.2	$	8,004.7	$	7,273.1

(1) Our 3.625% Senior Notes due September 15, 2022, were redeemed in full in July 2022. For additional information, please read Note 12, Indebtedness, to these condensed consolidated financial statements.

The fair values of each of our series of Senior Notes were determined through market, observable and corroborated sources. The changes in the fair values of our Senior Notes as of September 30, 2022, compared to December 31, 2021, are related to increases in U.S. treasury yields and wider credit spreads used to value our Senior Notes since December 31, 2021. For additional information related to our Senior Notes, please read Note 12, Indebtedness, to our consolidated financial statements included in our 2021 Form 10-K.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Financial Instruments

9 Months Ended

Sep. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Financial Instruments

The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included in cash and cash equivalents in our condensed consolidated balance sheets:


(In millions)	As of September 30, 2022		As of December 31, 2021
Commercial paper	$	3.2	$	247.6
Overnight reverse repurchase agreements	115.5		200.0
Money market funds	3,070.6		901.6
Short-term debt securities	2.5		283.0
Total	$	3,191.8	$	1,632.2

The carrying values of our commercial paper, including accrued interest, overnight reverse repurchase agreements, money market funds and short-term debt securities approximate fair value due to their short-term maturities.

Our marketable equity securities (gains) losses are recorded in other (income) expense, net in our condensed consolidated statements of income. The following tables summarize our marketable debt and equity securities, classified as available-for-sale:


	As of September 30, 2022
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Marketable debt securities
Corporate debt securities:
Current	$	833.6	$	—	$	(6.9)	$	826.7
Non-current	400.5		—		(8.1)		392.4
Government securities:
Current	412.1		0.1		(3.5)		408.7
Non-current	298.8		—		(5.5)		293.3
Mortgage and other asset backed securities:
Current	0.1		—		—		0.1
Non-current	177.6		—		(3.0)		174.6
Total marketable debt securities	$	2,122.7	$	0.1	$	(27.0)	$	2,095.8

Marketable equity securities

Marketable equity securities, non-current	$	1,133.8	$	—	$	(237.8)	$	896.0
Total marketable equity securities	$	1,133.8	$	—	$	(237.8)	$	896.0


	As of December 31, 2021
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Marketable debt securities
Corporate debt securities:
Current	$	723.6	$	0.1	$	(0.3)	$	723.4
Non-current	385.4		0.2		(0.8)		384.8
Government securities:
Current	817.0		—		(0.4)		816.6
Non-current	377.0		0.1		(1.0)		376.1
Mortgage and other asset backed securities:
Current	1.1		—		—		1.1
Non-current	131.8		—		(0.7)		131.1
Total marketable debt securities	$	2,435.9	$	0.4	$	(3.2)	$	2,433.1

Marketable equity securities
Marketable equity securities, current	$	33.9	$	9.9	$	—	$	43.8
Marketable equity securities, non-current	1,133.1		151.0		(279.4)		1,004.7
Total marketable equity securities	$	1,167.0	$	160.9	$	(279.4)	$	1,048.5

Summary of Contractual Maturities: Available-for-Sale Debt Securities

The estimated fair value and amortized cost of our marketable debt securities classified as available-for-sale by contractual maturity are summarized as follows:


	As of September 30, 2022				As of December 31, 2021
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,235.5	$	1,245.8	$	1,541.1	$	1,541.7
Due after one year through five years	848.3		864.0		868.2		870.2
Due after five years	12.0		12.9		23.8		24.0
Total marketable debt securities	$	2,095.8	$	2,122.7	$	2,433.1	$	2,435.9

The average maturity of our marketable debt securities classified as available-for-sale as of September 30, 2022 and December 31, 2021, was approximately 9 months and 10 months, respectively.

Proceeds from Marketable Debt Securities

The proceeds from maturities and sales of marketable debt securities and resulting realized gains and losses are summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Proceeds from maturities and sales	$	1,643.2	$	575.4	$	3,104.7	$	2,028.1
Realized gains	—		0.1		—		0.4
Realized losses	7.9		0.5		9.3		1.7

Realized losses for the three and nine months ended September 30, 2022 and 2021, primarily relate to sales of corporate bonds, agency mortgage-backed securities and other asset-backed securities.

Strategic Investments

As of September 30, 2022, our strategic investment portfolio was comprised of investments totaling $948.5 million which are included in investments and other assets in our condensed consolidated balance sheets. As of December 31, 2021, our strategic investment portfolio totaled $1,110.3 million and was included in other current assets and investments and other assets in our condensed consolidated balance sheets.

Our strategic investment portfolio includes investments in equity securities of certain biotechnology companies, which are reflected within our disclosures included in Note 7, Fair Value Measurements, to these condensed consolidated financial statements, venture capital funds where the underlying investments are in equity securities of certain biotechnology companies and non-marketable equity securities.

The decrease in our strategic investment portfolio as of September 30, 2022, was primarily due to a decrease in the fair value of our investments in Denali and Sangamo common stock.

For additional information on our investments in Denali, Sage and Sangamo common stock, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

Derivative Instruments

9 Months Ended

Sep. 30, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

Foreign Currency Forward Contracts - Hedging Instruments

Due to the global nature of our operations, portions of our revenue and operating expense are recorded in currencies other than the U.S. dollar. The value of revenue and operating expense measured in U.S. dollars is therefore subject to changes in foreign currency exchange rates. We enter into foreign currency forward contracts and foreign currency options with financial institutions with the primary objective to mitigate the impact of foreign currency exchange rate fluctuations on our international revenue and operating expense.

Foreign currency forward contracts and foreign currency options in effect as of September 30, 2022 and December 31, 2021, had durations of 1 to 15 months. These contracts have been designated as cash flow hedges and unrealized gains or losses on the portion of these foreign currency forward contracts that are included in the

effectiveness test are reported in accumulated other comprehensive income (loss) (referred to as AOCI in the tables below). Realized gains and losses of such contracts are recognized in revenue when the sale of product in the currency being hedged is recognized and in operating expense when the expense in the currency being hedged is recorded. We recognize all cash flow hedge reclassifications from accumulated other comprehensive income (loss) and fair value changes of excluded portions in the same line item in our condensed consolidated statements of income that have been impacted by the hedged item.

The notional amount of foreign currency forward contracts that were entered into to hedge forecasted revenue and operating expense is summarized as follows:


	Notional Amount
(In millions)	As of September 30, 2022		As of December 31, 2021
Euro	$	1,089.2	$	1,828.0
British pound	43.5		166.2
Swiss franc	37.8		—
Japanese yen	23.5		72.7
Canadian dollar	14.7		59.9
Total foreign currency forward contracts	$	1,208.7	$	2,126.8

The pre-tax portion of the fair value of these foreign currency forward contracts that were included in accumulated other comprehensive income (loss) in total equity is summarized as follows:



(In millions)	As of September 30, 2022		As of December 31, 2021
Unrealized gains	$	146.5	$	60.8
Unrealized (losses)	(2.2)		(7.0)
Net unrealized gains (losses)	$	144.3	$	53.8

We expect the net unrealized gains of approximately $144.3 million to be settled over the next 15 months, of which approximately $142.6 million of these net unrealized gains are expected to be settled over the next 12 months, with any amounts in accumulated other comprehensive income (loss) to be reported as an adjustment to revenue or operating expense. We consider the impact of our and our counterparties’ credit risk on the fair value of the contracts as well as the ability of each party to execute its contractual obligations. As of September 30, 2022 and December 31, 2021, credit risk did not materially change the fair value of our foreign currency forward contracts.

The following tables summarize the effect of foreign currency forward contracts designated as hedging instruments in our condensed consolidated statements of income:


For the Three Months Ended September 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2022		2021		Location	2022		2021
Revenue	$	77.7	$	(14.9)	Revenue	$	6.6	$	(0.7)
Operating expense	(0.8)		(0.3)		Operating expense	(0.1)		—

For the Nine Months Ended September 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2022		2021		Location	2022		2021
Revenue	$	143.2	$	(68.7)	Revenue	$	(0.8)	$	(4.5)
Operating expense	(3.5)		(0.3)		Operating expense	(0.4)		(0.4)

Net Investment Hedges - Hedging Instruments

In February 2012 we entered into a joint venture agreement with Samsung BioLogics establishing an entity, Samsung Bioepis, to develop, manufacture and market biosimilar products. In June 2018 we exercised our option under our joint venture agreement to increase our ownership percentage in Samsung Bioepis from approximately 5.0% to approximately 49.9%. The share purchase transaction was completed in November 2018 and, upon closing,

we paid 759.5 billion South Korean won ($676.6 million) to Samsung BioLogics. Our investment in the equity of Samsung Bioepis related to this transaction was exposed to the currency fluctuations in the South Korean won.

In order to mitigate the currency fluctuations between the U.S. dollar and South Korean won, we entered into foreign currency forward contracts. These contracts were designated as net investment hedges. In April 2022 we completed the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics and closed these foreign currency forward contracts. Upon completing this sale, the cumulative gains on our net investment hedges of $57.0 million were reclassified from accumulated other comprehensive income (loss) and reflected within the total pre-tax gain recognized from the sale, which was recorded in other (income) expense, net in our condensed consolidated statements of income. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.

Prior to the sale of our 49.9% equity interest in Samsung Bioepis, we recognized changes in the spot exchange rate of these foreign currency forward contracts in accumulated other comprehensive income (loss). The pre-tax portion of the fair value of these foreign currency forward contracts that were included in accumulated other comprehensive income (loss) in total equity reflected net gains of $10.6 million as of December 31, 2021. We excluded fair value changes related to the forward rate from our hedging relationship and amortized the forward points in other (income) expense, net in our condensed consolidated statements of income over the term of the contract. The pre-tax portion of the fair value of the forward points that were included in accumulated other comprehensive income (loss) in total equity reflected net losses of $3.6 million as of December 31, 2021.

The following tables summarize the effect of our net investment hedges in our condensed consolidated financial statements:


For the Three Months Ended September 30,
Net Gains/(Losses) Recognized in Other Comprehensive Income (Effective Portion) (in millions)					Net Gains/(Losses) Recognized in Other Comprehensive Income (Amounts Excluded from Effectiveness Testing) (in millions)					Net Gains/(Losses) Recognized in Net Income (Amounts Excluded from Effectiveness Testing) (in millions)
Location	2022		2021		Location	2022		2021		Location	2022		2021
Gains (losses) on net investment hedges(1)	$	—	$	24.9	Gains (losses) on net investment hedges(1)	$	—	$	—	Other (income) expense(1)	$	—	$	—

For the Nine Months Ended September 30,
Net Gains/(Losses) Recognized in Other Comprehensive Income (Effective Portion) (in millions)					Net Gains/(Losses) Recognized in Other Comprehensive Income (Amounts Excluded from Effectiveness Testing) (in millions)					Net Gains/(Losses) Recognized in Net Income (Amounts Excluded from Effectiveness Testing) (in millions)
Location	2022		2021		Location	2022		2021		Location	2022		2021
Gains (losses) on net investment hedges(1)	$	20.4	$	46.1	Gains (losses) on net investment hedges(1)	$	(3.2)	$	(1.1)	Other (income) expense(1)	$	(4.6)	$	0.1

(1) Beginning in the second quarter of 2022 we no longer hold net investment hedges as they were closed with the sale of our 49.9% equity interest in Samsung Bioepis in April 2022. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.

For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 18, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Foreign Currency Forward Contracts - Other Derivative Instruments

We also enter into other foreign currency forward contracts, usually with durations of one month or less, to mitigate the foreign currency risk related to certain balance sheet positions. We have not elected hedge accounting for these transactions.

The aggregate notional amount of these outstanding foreign currency forward contracts was $1,285.4 million and $1,268.0 million as of September 30, 2022 and December 31, 2021, respectively. Net losses of $36.5 million and $85.8 million related to these contracts were recorded as a component of other (income) expense, net for the three and nine months ended September 30, 2022, respectively, compared to net losses of $13.5 million and $26.1 million, respectively, in the prior year comparative periods.

Summary of Derivative Instruments

While certain of our derivative instruments are subject to netting arrangements with our counterparties, we do not offset derivative assets and liabilities in our condensed consolidated balance sheets. The amounts in the table below would not be substantially different if the derivative assets and liabilities were offset.

The following table summarizes the fair value and presentation in our condensed consolidated balance sheets of our outstanding derivative instruments, including those designated as hedging instruments:


(In millions)	Balance Sheet Location	As of September 30, 2022		As of December 31, 2021
Cash Flow Hedging Instruments:
Asset derivative instruments	Other current assets	$	158.2	$	66.2
	Investments and other assets	5.0		5.5
Liability derivative instruments	Accrued expense and other	2.6		6.6


Net Investment Hedging Instruments:(1)
Asset derivative instruments	Other current assets	21.4		4.1






Other Derivative Instruments:
Asset derivative instruments	Other current assets	11.3		5.1
Liability derivative instruments	Accrued expense and other	20.2		4.2

(1) Beginning in the second quarter of 2022 we no longer hold net investment hedges as they were closed with the sale of our 49.9% equity interest in Samsung Bioepis in April 2022. Amount represents unsettled balance of our closed net investment hedges. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.

Property, Plant and Equipment	9 Months Ended
Property, Plant and Equipment	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Accumulated depreciation on property, plant and equipment was $2,098.0 million and $2,006.6 million as of September 30, 2022 and December 31, 2021, respectively. For the three and nine months ended September 30, 2022, depreciation expense totaled $64.2 million and $207.7 million, respectively, compared to $65.1 million and $168.7 million, respectively, in the prior year comparative periods. Solothurn, Switzerland Manufacturing Facility In order to support our future growth and drug development pipeline, we are building a large-scale biologics manufacturing facility in Solothurn, Switzerland. Upon completion, this facility will include 393,000 square feet related to a large-scale biologics manufacturing facility, 290,000 square feet of warehouse, utilities and support space and 51,000 square feet of administrative space. As of September 30, 2022 and December 31, 2021, we had approximately $701.0 million and $677.0 million, respectively, capitalized as construction in progress related to this facility. In the second quarter of 2021, a portion of the facility received a Good Manufacturing Practice multi-product license from the Swiss Agency for Therapeutic Products, resulting in approximately $1.2 billion of fixed assets being placed in service during the second quarter of 2021. In April 2022 the FDA approved the Prior Approval Supplement for the Solothurn facility for ADUHELM. We estimate the second manufacturing suite at the Solothurn facility will be operational during the second half of 2023. 125 Broadway Building Sale In September 2022 we completed the sale of our building and land parcel located at 125 Broadway, Cambridge, MA (125 Broadway) for an aggregate sales price of approximately $603.0 million, which is inclusive of a $10.8 million tenant allowance. This sale resulted in a pre-tax gain on sale of approximately $503.7 million, net of transaction costs, which is reflected within gain on sale of building in our condensed consolidated statements of income for the three and nine months ended September 30, 2022. This transaction included approximately $79.2 million of property, plant and equipment, net, which comprised of approximately $72.6 million for buildings, approximately $1.6 million for land and approximately $5.0 million for machinery and equipment.

Leases	9 Months Ended
Leases	Sep. 30, 2022
Leases [Abstract]
Leases	LEASES 125 Broadway Building Sale and Leaseback Transaction in connection with the sale of our building at 125 Broadway, we simultaneously leased back the building for a term of approximately 5.5 years, which resulted in the recognition of approximately $168.2 million in new lease liabilities and right-of-use assets recorded within our condensed consolidated balance sheets as of September 30, 2022. The sale and immediate leaseback of this building qualified for sale and leaseback treatment and is classified as an operating lease. For additional information on the sale of our building, please read Note 10, Property, Plant and Equipment, to these condensed consolidated financial statements. 300 Binney Street Lease Modification In September 2022 we entered into an agreement to partially terminate a portion of our lease located at 300 Binney Street, Cambridge MA, as well as to reduce the lease term for the majority of the remaining space. The agreement was driven by our 2022 efforts to reduce costs by consolidating real estate locations. The transaction was treated as a lease modification as of the effective date and resulted in the derecognition of right of use assets of approximately $47.4 million and lease liabilities of approximately $52.7 million, which resulted in a gain of approximately $5.3 million, which was recorded within restructuring charges in our condensed consolidated statements of income for the three and nine months ended September 30, 2022.

Indebtedness	9 Months Ended
Indebtedness	Sep. 30, 2022
Debt Disclosure [Abstract]
Indebtedness	3.625% Senior Notes due September 15, 2022 On September 15, 2015, we issued $1.0 billion aggregate principal amount of our 3.625% Senior Notes due September 15, 2022, at 99.920% of par. Our 3.625% Senior Notes were senior unsecured obligations. In July 2022 we redeemed our 3.625% Senior Notes prior to their maturity and recognized a net pre-tax charge of approximately $2.4 million upon the extinguishment of these Senior Notes, which primarily reflects the payment of an early call premium as well as the write-off of remaining unamortized original debt issuance costs and discount balances. These charges were recognized as interest expense in other (income) expense, net in our condensed consolidated statements of income for the three and nine months ended September 30, 2022. Exchange Offer In February 2021 we completed our Exchange Offer of our tendered 2045 Senior Notes for our 2051 Senior Notes and cash, and an offer to purchase our tendered 2045 Senior Notes for cash. An aggregate principal amount of approximately $624.6 million of our 2045 Senior Notes was exchanged for an aggregate principal amount of approximately $700.7 million of our 2051 Senior Notes and aggregate cash payments of approximately $151.8 million. Our Exchange Offer has been accounted for as a debt modification; as such, the cash component has been reflected as additional debt discount and is amortized as an adjustment to interest expense over the term of our 2051 Senior Notes. In addition, we redeemed an aggregate principal amount of approximately $8.9 million of our 2045 Senior Notes for aggregate cash payments of approximately $12.1 million, excluding accrued and unpaid interest. The redemption has been accounted for as a debt extinguishment; as such, we recognized a pre-tax charge of $3.2 million upon the extinguishment of such 2045 Senior Notes. This charge, which was recognized in interest expense in other (income) expense, net in our condensed consolidated statements of income for the nine months ended September 30, 2021, reflects the payment of an early call premium and the write-off of the remaining unamortized original debt issuance costs and discount balances associated with such 2045 Senior Notes. Upon settlement, we also made aggregate cash payments of approximately $13.8 million to settle all accrued and unpaid interest from the last interest payment date on our 2045 Senior Notes that were exchanged or redeemed. We incurred approximately $6.1 million of costs associated with our Exchange Offer, which was recognized in interest expense in other (income) expense, net in our condensed consolidated statements of income for the nine months ended September 30, 2021.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

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+ Details

Equity

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Equity

Share Repurchases

In October 2020 our Board of Directors authorized a program to repurchase up to $5.0 billion of our common stock (2020 Share Repurchase Program). Our 2020 Share Repurchase Program does not have an expiration date. All share repurchases under our 2020 Share Repurchase Program will be retired. Under our 2020 Share Repurchase Program, we repurchased and retired approximately 1.2 million and 3.6 million shares of our common stock at a cost of approximately $250.0 million and $750.0 million during the three and nine months ended September 30, 2022, respectively. During the three and nine months ended September 30, 2021, we repurchased and retired approximately 2.2 million and 6.0 million shares of our common stock at a cost of approximately $750.0 million and $1.8 billion, respectively. Approximately $2.1 billion remained available under our 2020 Share Repurchase Program as of September 30, 2022.

Accumulated Other Comprehensive Income (Loss)

The following tables summarize the changes in accumulated other comprehensive income (loss), net of tax by component:


(In millions)	Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax		Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Gains (Losses) on Net Investment Hedges, Net of Tax(1)		Unrealized gains (losses) on pension benefit obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2021	$	(2.2)	$	53.8	$	25.5	$	(44.8)	$	(139.0)	$	(106.7)
Other comprehensive income (loss) before reclassifications	(26.4)		204.5		12.6		4.2		(154.5)		40.4
Amounts reclassified from accumulated other comprehensive income (loss)	7.4		(125.5)		(38.1)		—		58.9		(97.3)
Net current period other comprehensive income (loss)	(19.0)		79.0		(25.5)		4.2		(95.6)		(56.9)
Balance, September 30, 2022	$	(21.2)	$	132.8	$	—	$	(40.6)	$	(234.6)	$	(163.6)


(In millions)	Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax		Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Gains (Losses) on Net Investment Hedges, Net of Tax		Unrealized gains (losses) on pension benefit obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2020	$	1.4	$	(179.0)	$	(8.5)	$	(66.3)	$	(46.6)	$	(299.0)
Other comprehensive income (loss) before reclassifications	(2.5)		143.0		35.3		3.9		(80.3)		99.4
Amounts reclassified from accumulated other comprehensive income (loss)	1.1		62.0		(0.1)		—		—		63.0
Net current period other comprehensive income (loss)	(1.4)		205.0		35.2		3.9		(80.3)		162.4
Balance, September 30, 2021	$	—	$	26.0	$	26.7	$	(62.4)	$	(126.9)	$	(136.6)

The following table summarizes the amounts reclassified from accumulated other comprehensive income (loss):


(In millions)	Income Statement Location	Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)
		For the Three Months Ended September 30,				For the Nine Months Ended September 30,
		2022		2021		2022		2021
Gains (losses) on securities available for sale	Other (income) expense	$	(8.0)	$	(0.4)	$	(9.4)	$	(1.3)
	Income tax benefit (expense)	1.7		0.1		2.0		0.3

Gains (losses) on cash flow hedges	Revenue	77.7		(14.9)		143.2		(68.7)
	Operating expense	(0.8)		(0.3)		(3.5)		(0.3)
	Other (income) expense	—		—		(0.2)		0.1
	Income tax benefit (expense)	(7.8)		1.5		(14.0)		6.8

Gains (losses) on net investment hedges(1)	Other (income) expense	—		—		38.1		0.1


Currency Translation Adjustments	Other (income) expense	—		—		(58.9)		—
Total reclassifications, net of tax		$	62.8	$	(14.0)	$	97.3	$	(63.0)

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Earnings per Share

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Earnings per Share

Basic and diluted shares outstanding used in our earnings per share calculation are calculated as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Numerator:
Net income attributable to Biogen Inc.	$	1,134.7	$	329.2	$	2,496.5	$	1,187.9
Denominator:
Weighted average number of common shares outstanding	144.4		148.0		145.8		149.9
Effect of dilutive securities:

Time-vested restricted stock units	0.3		0.4		0.3		0.2
Market stock units	—		0.1		—		0.1
Performance stock units settled in stock	0.1		0.1		0.1		0.1
Dilutive potential common shares	0.4		0.6		0.4		0.4
Shares used in calculating diluted earnings per share	144.8		148.6		146.2		150.3

Amounts excluded from the calculation of net income per diluted share because their effects were anti-dilutive were insignificant.

Share-based Payments

9 Months Ended

Sep. 30, 2022

Share-based Payment Arrangement [Abstract]

Share-based Payments

Share-based Compensation Expense

The following table summarizes share-based compensation expense included in our condensed consolidated statements of income:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Research and development	$	24.5	$	19.5	$	72.6	$	72.2
Selling, general and administrative	46.5		42.6		129.3		127.8

Subtotal	71.0		62.1		201.9		200.0
Capitalized share-based compensation costs	(2.0)		(1.9)		(7.1)		(6.3)
Share-based compensation expense included in total cost and expense	69.0		60.2		194.8		193.7
Income tax effect	(13.0)		(10.9)		(36.0)		(35.8)
Share-based compensation expense included in net income attributable to Biogen Inc.	$	56.0	$	49.3	$	158.8	$	157.9

The following table summarizes share-based compensation expense associated with each of our share-based compensation programs:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Market stock units	$	4.0	$	9.7	$	11.4	$	35.5
Time-vested restricted stock units	48.7		38.8		150.4		121.9


Performance stock units settled in stock	10.5		4.9		22.1		14.2
Performance stock units settled in cash	5.4		4.4		7.9		13.9
Employee stock purchase plan	2.4		4.3		10.1		14.5

Subtotal	71.0		62.1		201.9		200.0
Capitalized share-based compensation costs	(2.0)		(1.9)		(7.1)		(6.3)
Share-based compensation expense included in total cost and expense	$	69.0	$	60.2	$	194.8	$	193.7

We estimate the fair value of our obligations associated with our performance stock units settled in cash at the end of each reporting period through expected settlement. Cumulative adjustments to these obligations are recognized each quarter to reflect changes in the stock price and estimated outcome of the performance-related conditions.

Income Taxes

9 Months Ended

Sep. 30, 2022

Income Tax Disclosure [Abstract]

Income Taxes

Tax Rate

A reconciliation between the U.S. federal statutory tax rate and our effective tax rate is summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2022		2021		2022		2021
Statutory rate	21.0	%	21.0	%	21.0	%	21.0	%
State taxes	1.9		0.3		1.1		0.9
Taxes on foreign earnings	(3.4)		(20.2)		(4.4)		(11.5)
Tax credits	(1.4)		(7.1)		(1.5)		(4.1)
Purchased intangible assets	0.1		(6.2)		0.2		(1.4)



GILTI	0.8		2.6		0.5		1.6



Sale of Samsung Bioepis	(0.8)		—		(1.9)		—
Litigation settlement agreement	(1.2)		—		3.1		—
Neurimmune tax impacts	—		(0.5)		2.8		(36.4)
International reorganization	—		—		(1.7)		—
Other	0.2		1.2		0.2		0.7
Effective tax rate	17.2	%	(8.9)	%	19.4	%	(29.2)	%

Changes in Tax Rate

For the three and nine months ended September 30, 2022, compared to the same periods in 2021, the increases in our effective tax rates include the tax impacts on the sale of one of our buildings and the favorable prior year tax effects of changes in the value of our equity investments, where we recorded unrealized losses, and the BIIB111 and BIIIB112 impairment charges. The tax effects of this change in value of our equity investments were recorded discretely as changes in value of equity investments cannot be forecasted.

For the nine months ended September 30, 2022, compared to the same period in 2021, the increase in our effective tax rate also reflects the net effects of the Neurimmune SubOne AG (Neurimmune) matters, as discussed below, and the litigation settlement agreement.

During the second quarter of 2021 we recorded a net deferred tax asset in Switzerland of approximately $490.0 million on Neurimmune's tax basis in ADUHELM, the realization of which is dependent on future sales of ADUHELM. During the fourth quarter of 2021, due to reduced future expected revenue associated with ADUHELM, we recorded a valuation allowance of approximately $390.0 million.

During the first quarter of 2022, upon issuance of the final NCD related to ADUHELM, we recorded an additional valuation allowance of approximately $85.0 million to reduce the net value of this deferred tax asset to zero. These adjustments to our deferred tax assets and their valuation allowances are each recorded with an equal and offsetting amount assigned to net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income, resulting in a zero net impact to net income attributable to Biogen Inc.

For additional information on the litigation settlement agreement, please read Note 20, Litigation, to these condensed consolidated financial statements.

For additional information on our collaboration arrangement with Neurimmune, please read Note 19, Investments in Variable Interest Entities, to these condensed consolidated financial statements.

Accounting for Uncertainty in Income Taxes

We and our subsidiaries are routinely examined by various taxing authorities. We file income tax returns in various U.S. states and in U.S. federal and other foreign jurisdictions. With few exceptions, we are no longer subject to U.S. federal tax examination for years before 2017 or state, local or non-U.S. income tax examinations for years before 2012.

The U.S. Internal Revenue Service and other national tax authorities routinely examine our intercompany transfer pricing with respect to intellectual property related transactions and it is possible that they may disagree with one or more positions we have taken with respect to such valuations.

It is reasonably possible that we will adjust the value of our uncertain tax positions related to certain transfer pricing, collaboration matters and other issues as we receive additional information from various taxing authorities, including reaching settlements with such authorities.

We estimate that it is reasonably possible that our gross unrecognized tax benefits, exclusive of interest, could

decrease by up to approximately $500.0 million, including approximately $455.0 million related to the unrecognized

tax benefits related to Neurimmune's tax basis in ADUHELM, in the next 12 months as a result of various audit

closures, settlements and expiration of the statute of limitations. Any changes to our gross unrecognized tax benefits related to Neurimmune's tax basis in ADUHELM would result in a zero net impact to net income attributable to Biogen, Inc., as w

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Other Consolidated Financial Statement Detail

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Other Consolidated Financial Statement Detail

Other (Income) Expense, Net

Components of other (income) expense, net, are summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Gain on sale of equity interest in Samsung Bioepis(1)	$	—	$	—	$	(1,505.4)	$	—
Litigation settlement agreement	—		—		900.0		—
Interest income	(23.9)		(2.6)		(39.4)		(8.2)
Interest expense	59.9		66.3		191.8		187.3
(Gains) losses on investments, net	(101.8)		424.5		167.5		707.2
Foreign exchange (gains) losses, net	11.5		13.7		39.0		23.1
Other, net	(1.7)		1.0		25.2		4.0
Total other (income) expense, net	$	(56.0)	$	502.9	$	(221.3)	$	913.4

(1) Reflects the pre-tax gain, net of transaction costs, recognized from the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics in April 2022. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.

(Gains) losses on investments, net, as reflected in the table above, relate to debt securities, equity securities of certain biotechnology companies, venture capital funds where the underlying investments are in equity securities of certain biotechnology companies and non-marketable equity securities.

During the second quarter of 2022 we recorded a pre-tax charge of $900.0 million, plus estimated fees and expenses, related to a litigation settlement agreement to resolve a qui tam litigation relating to conduct prior to 2015. This charge is included within other (income) expense, net in our condensed consolidated statements of income for the nine months ended September 30, 2022. For additional information on the litigation settlement agreement, please read Note 20, Litigation, to these condensed consolidated financial statements.

The following table summarizes our (gains) losses on investments, net that relate to our equity securities held during the following periods:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Net (gains) losses recognized on equity securities	$	(109.8)	$	424.2	$	158.1	$	705.9
Less: Net (gains) losses realized on equity securities	(0.5)		(2.7)		—		(9.3)
Net unrealized (gains) losses recognized on equity securities	$	(109.3)	$	426.9	$	158.1	$	715.2

The net unrealized gains recognized during the three months ended September 30, 2022, primarily reflect an increase in the aggregate fair value of our investments in Sage, Ionis Pharmaceuticals, Inc. (Ionis), Sangamo and Denali common stock of approximately $112.5 million.

The net unrealized losses recognized during the nine months ended September 30, 2022, primarily reflect a decrease in the aggregate fair value of our investments in Denali and Sangamo common stock of approximately $198.0 million.

Accrued Expense and Other

Accrued expense and other consists of the following:


(In millions)	As of September 30, 2022		As of December 31, 2021
Litigation settlement agreement(1)	$	900.0	$	—
Revenue-related reserves for discounts and allowances	854.5		802.1
Collaboration expense	260.1		324.7
Royalties and licensing fees	208.6		234.7
Employee compensation and benefits	313.5		345.1


Other	769.2		828.6
Total accrued expense and other	$	3,305.9	$	2,535.2

(1) During the second quarter of 2022 we recorded a pre-tax charge of $900.0 million, plus estimated fees and expenses, related to a litigation settlement agreement to resolve a qui tam litigation relating to conduct prior to 2015. For additional information on the litigation settlement agreement, please read Note 20, Litigation, to these condensed consolidated financial statements.

Other Long-term Liabilities

Other long-term liabilities were $1,198.1 million and $1,320.5 million as of September 30, 2022 and December 31, 2021, respectively, and included accrued income taxes totaling $559.7 million and $664.5 million, respectively.

Collaborative and Other Relationships

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaborative and Other Relationships

Eisai Co., Ltd.

Lecanemab Collaboration

We have a collaboration agreement with Eisai Co., Ltd. (Eisai) to jointly develop and commercialize lecanemab (BAN2401), an anti-amyloid antibody, and elenbecestat, the oral BACE (base amyloid cleaving enzyme) inhibitor, two Eisai product candidates for the potential treatment of Alzheimer's disease (the Lecanemab Collaboration). In September 2019 we and Eisai discontinued the global Phase 3 studies of elenbecestat in early Alzheimer's disease.

Eisai serves as the lead of lecanemab development and regulatory submissions globally with both companies co-commercializing and co-promoting the product, and Eisai having final decision-making authority. All costs, including research, development, sales and marketing expense, are shared equally between us and Eisai. If lecanemab receives marketing approval, we and Eisai will co-promote lecanemab and share profits or losses equally. In March 2022 we extended our supply agreement related to lecanemab from five years to ten years for the manufacture of lecanemab drug substance and drug product.

In May 2022 Eisai completed the submission of a Biologics License Application (BLA) to the FDA for the accelerated approval of lecanemab. In July 2022 the FDA accepted the BLA and granted Priority Review with a Prescription Drug User Fee Act action date of January 6, 2023.

The Lecanemab Collaboration also provided Eisai with an option to jointly develop and commercialize ADUHELM (aducanumab) (ADUHELM Option). In October 2017 Eisai exercised its ADUHELM Option and we entered into a new collaboration agreement for the joint development and commercialization of ADUHELM (the ADUHELM Collaboration Agreement).

A summary of development and sales and marketing expense related to the Lecanemab Collaboration is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total development expense incurred by the collaboration related to the advancement of lecanemab and elenbecestat	$	109.3	$	118.4	$	264.9	$	236.1
Biogen's share of lecanemab and elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income	54.7		59.2		132.5		118.0
Total sales and marketing expense incurred by the Lecanemab Collaboration	29.0		5.6		68.3		15.6
Biogen's share of lecanemab and elenbecestat sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	14.5		2.8		34.2		7.8

For additional information on our Lecanemab Collaboration, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

ADUHELM Collaboration Agreement

Under our initial ADUHELM Collaboration Agreement, we would lead the ongoing development of ADUHELM, and we and Eisai would co-promote ADUHELM with a region-based profit split. Beginning January 1, 2019, Eisai was reimbursing us for 45.0% of development costs incurred by the collaboration for the advancement of ADUHELM (ADUHELM development expense).

In June 2021 ADUHELM was granted accelerated approval by the FDA for the treatment of Alzheimer's disease and had its first commercial sale. As a result of the launch of ADUHELM in the U.S., we made a $100.0 million milestone payment to Neurimmune. For the nine months ended September 30, 2021, we recognized net profit-sharing income of $45.0 million to reflect Eisai's 45.0% share of the $100.0 million milestone payment, which was recorded in collaboration profit (loss) sharing in our condensed consolidated statements of income.

In March 2022 we amended our ADUHELM Collaboration Agreement with Eisai. Effective March 2022, we have sole decision making and commercialization rights worldwide on ADUHELM and beginning January 1, 2023, Eisai will receive a tiered royalty based on net sales of ADUHELM, rather than sharing global profits and losses. Eisai's share of development, commercialization and manufacturing expense is limited to $335.0 million for the period from January 1, 2022 to December 31, 2022. As of September 30, 2022, Eisai's portion of these expenses was approximately $300.0 million. Once this limit is achieved, we will be responsible for all ADUHELM related development costs. After the tiered royalty model commences on January 1, 2023, Eisai will not participate in ADUHELM’s economics beyond these royalties.

A summary of development expense, sales and marketing expense and milestone payments related to the ADUHELM Collaboration Agreement is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total ADUHELM development expense	$	34.6	$	43.7	$	116.0	$	132.8
Biogen's share of ADUHELM development expense reflected in research and development expense in our condensed consolidated statements of income	19.0		24.0		63.8		73.0
Total ADUHELM sales and marketing expense incurred by the ADUHELM Collaboration Agreement	(8.0)		154.3		127.8		391.7
Biogen's share of ADUHELM sales and marketing expense reflected in selling, general and administrative expense and collaboration profit (loss) sharing in our condensed consolidated statements of income	(3.9)		83.3		68.1		211.2
Total ADUHELM collaboration third party milestones	—		—		—		100.0
Biogen's share of reimbursement from Eisai of ADUHELM milestone payments reflected in collaboration profit (loss) sharing in our condensed consolidated statements of income	—		—		—		45.0

Co-promotion Profits and Losses

In the U.S. we recognize revenue on sales to third parties as a component of product revenue, net in our condensed consolidated statements of income. We also record the related cost of revenue and sales and marketing expense in our condensed consolidated statements of income as these costs are incurred. Payments made to and received from Eisai for its 45.0% share of the co-promotion profits or losses in the U.S. are recognized in collaboration profit (loss) sharing in our condensed consolidated statements of income. For the three and nine months ended September 30, 2022, we recognized a net reduction to our operating expense of $3.4 million and $214.0 million, respectively, to reflect Eisai's 45.0% share of net collaboration losses in the U.S., compared to $50.6 million and $90.7 million, respectively, in the prior year comparative periods.

In addition, we and Eisai co-promote AVONEX, TYSABRI and TECFIDERA in Japan in certain settings and Eisai distributes AVONEX, TYSABRI, TECFIDERA and PLEGRIDY in India and other Asia-Pacific markets, excluding China.

During the first quarter of 2022 we recorded approximately $275.0 million of gross charges associated with inventory and purchase commitments in excess of forecasted demand related to ADUHELM. For the nine months ended September 30, 2022, we have also recorded approximately $76.0 million of aggregate gross idle capacity charges related to ADUHELM.

We have recognized approximately $177.0 million related to Eisai's 45.0% share of inventory and idle capacity charges in collaboration profit (loss) sharing within our condensed consolidated statements of income for the nine months ended September 30, 2022.

Amounts receivable from Eisai related to the agreements discussed above were $110.6 million and $285.4 million as of September 30, 2022 and December 31, 2021, respectively. Amounts payable to Eisai related to the agreements discussed above were $81.7 million and $46.5 million as of September 30, 2022 and December 31, 2021, respectively.

For additional information on the ADUHELM Collaboration Agreement, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

UCB

We have a collaboration agreement with UCB to jointly develop and commercialize dapirolizumab pegol, an anti-CD40L pegylated Fab, for the potential treatment of systemic lupus erythematosus and other future agreed indications. Either we or UCB may propose development of dapirolizumab pegol in additional indications. If the parties do not agree to add an indication as an agreed indication to the collaboration, we or UCB may, at the sole expense of the applicable party, pursue development in such excluded indication(s), subject to an opt-in right of the non-pursuing party after proof of clinical activity.

All costs incurred for agreed indications, including research, development, sales and marketing expense, are shared equally between us and UCB. If marketing approval is obtained, we and UCB will co-promote dapirolizumab pegol and share profits equally.

A summary of development expense related to the UCB collaboration agreement is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total UCB collaboration development expense	$	18.3	$	16.5	$	51.5	$	49.5
Biogen's share of UCB development expense reflected in research and development expense in our condensed consolidated statements of income	9.1		8.2		25.7		24.8

Sage Therapeutics, Inc.

In November 2020 we entered into a global collaboration and license agreement with Sage to jointly develop and commercialize BIIB125 (zuranolone) for the potential treatment of major depressive disorder and postpartum depression and BIIB124 (SAGE-324) for the potential treatment of essential tremor with potential in other neurological conditions such as epilepsy.

Under this collaboration, both companies will share equal responsibility and costs for development as well as profits and losses for commercialization in the U.S. Outside of the U.S., we are responsible for development and commercialization, excluding Japan, Taiwan and South Korea, with respect to zuranolone and may pay Sage potential tiered royalties in the high teens to low twenties.

A summary of development and sales and marketing expense related to this collaboration is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total Sage collaboration development expense	$	40.9	$	40.8	$	130.4	$	134.9
Biogen's share of Sage development expense reflected in research and development expense in our condensed consolidated statements of income	20.5		20.4		65.2		67.3
Total Sage sales and marketing expense incurred by the collaboration	28.5		7.4		69.9		23.2
Biogen's share of Sage sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	14.2		3.7		34.9		11.6

Denali Therapeutics Inc.

In August 2020 we entered into a collaboration and license agreement with Denali to co-develop and co-commercialize Denali's small molecule inhibitors of leucine-rich repeat kinase 2 (LRRK2) for Parkinson's disease. Under this collaboration, both companies share responsibility and costs for global development based on specified percentages as well as profits and losses for commercialization in the U.S. and China. Outside the U.S. and China we are responsible for commercialization and may pay Denali potential tiered royalties.

In addition to the LRRK2 program, we also have an exclusive option to license two preclinical programs from Denali’s Transport Vehicle platform, including its Antibody Transport Vehicle (ATV): ATV enabled anti-amyloid beta program and a second program utilizing its Transport Vehicle technology. Further, we have the right of first negotiation on two additional ATV-enabled therapeutics for indications within specific neurodegenerative diseases, should Denali decide to seek a collaboration for such programs.

In October 2022 we and Denali announced the initiation of the Phase 3 LIGHTHOUSE study for BIIB122 (DNL151), a small molecule inhibitor of LRRK2 for the potential treatment of Parkinson's disease.

A summary of development expense related to this collaboration is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total Denali collaboration development expense	$	19.9	$	8.5	$	58.0	$	27.2
Biogen's share of Denali development expense reflected in research and development expense in our condensed consolidated statements of income	11.4		5.1		33.5		16.3

Sangamo Therapeutics, Inc.

In February 2020 we entered into a collaboration and license agreement with Sangamo to develop and commercialize ST-501 for tauopathies, including Alzheimer's disease; ST-502 for synucleinopathies, including Parkinson’s disease; a third neuromuscular disease target; and up to nine additional neurological disease targets to be identified and selected within a five-year period. The companies are leveraging Sangamo’s proprietary zinc finger

protein technology delivered via adeno-associated virus to modulate the expression of key genes involved in neurological diseases.

Under this collaboration, we may pay Sangamo tiered royalties on potential net sales of any products developed under this collaboration in the high single digit to sub-teen percentages.

A summary of development expense related to this collaboration is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total Sangamo collaboration development expense	$	5.5	$	6.2	$	16.4	$	16.4
Biogen's share of Sangamo development expense reflected in research and development expense in our condensed consolidated statements of income	3.1		1.9		10.2		9.5

InnoCare Pharma Limited

In July 2021 we entered into a collaboration and license agreement with InnoCare Pharma Limited (InnoCare) for orelabrutinib, an oral small molecule Bruton’s tyrosine kinase inhibitor for the potential treatment of MS. Orelabrutinib is currently being studied in a multi-country, placebo-controlled Phase 2 trial in relapsing-remitting MS. Under the terms of the collaboration, we have exclusive rights to orelabrutinib in the field of MS worldwide and certain autoimmune diseases outside of China (including Hong Kong, Macau and Taiwan), while InnoCare retains exclusive worldwide rights to orelabrutinib in the field of oncology and certain autoimmune diseases in China (including Hong Kong, Macau and Taiwan).

In connection with the closing of this transaction in August 2021 we made an upfront payment of $125.0 million that was recorded as research and development expense in our condensed consolidated statements of income. We may also pay InnoCare up to approximately $812.5 million in potential development milestones and potential commercial payments should this collaboration achieve certain development, commercial milestones and sales thresholds. In addition, we may pay InnoCare tiered royalties on potential net sales of any products developed under this collaboration in the low to high teen percentages.

Other Research and Discovery Arrangements

These arrangements may include the potential for future milestone payments based on the achievement of certain clinical and commercial development payable over a period of several years.

Other

For the three and nine months ended September 30, 2022, we recorded $14.0 million and $51.5 million, respectively, as research and development expense in our condensed consolidated statements of income related to other research and discovery related arrangements, compared to $7.7 million and $84.9 million, respectively, in the prior year comparative periods.

Samsung Bioepis Co., Ltd.

Joint Venture Agreement

In February 2012 we entered into a joint venture agreement with Samsung BioLogics establishing an entity, Samsung Bioepis, to develop, manufacture and market biosimilar products.

In April 2022 we completed the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics. Under the terms of this transaction, we received approximately $1.0 billion in cash at closing and expect to receive approximately $1.3 billion in cash to be deferred over two payments of approximately $812.5 million due at the first anniversary and approximately $437.5 million due at the second anniversary of the closing of this transaction.

As part of the transaction, we are also eligible to receive up to an additional $50.0 million upon the achievement of certain commercial milestones. Our policy for contingent payments of this nature is to recognize them in the period that they become realizable, which is generally the same period in which they are earned.

Prior to this sale, we recognized our share of the results of operations related to our investment in Samsung Bioepis under the equity method of accounting one quarter in arrears when the results of the entity became available, which was reflected as equity in (income) loss of investee, net of tax in our condensed consolidated statements of income.

Upon investment, the equity method of accounting required us to identify and allocate differences between the fair value of our investment and the carrying value of our interest in the underlying net assets of the investee. These basis differences were being amortized over their economic life until the completion of the sale in April 2022, as discussed above. The total basis difference was approximately $675.0 million and related to inventory, developed technology, IPR&D and deferred tax balances. The basis differences related to inventory were amortized, net of tax, over their estimated useful lives of 1.5 years, and the basis differences related to developed technology and IPR&D for marketed products were being amortized, net of tax, over their estimated useful lives of 15 years.

For the nine months ended September 30, 2022, we recognized net income on our investment of $2.6 million, reflecting our share of Samsung Bioepis' operating profits, net of tax totaling $17.0 million, offset by amortization of basis differences totaling $14.4 million. This amount reflects our share of results prior to the sale of Samsung Bioepis as the results are recognized one quarter in arrears. Following the sale of Samsung Bioepis we no longer recognize gains or losses associated with Samsung Bioepis' results of operations and amortization related to basis differences.

For the three and nine months ended September 30, 2021, we recognized net income on our investment of $1.1 million and $17.2 million, respectively, reflecting our share of Samsung Bioepis' operating profits, net of tax totaling $8.9 million and $39.5 million, respectively, offset by amortization of basis differences totaling $7.8 million and $22.3 million, respectively.

As of December 31, 2021, the carrying value of our investment in Samsung Bioepis totaled 713.3 billion South Korean won ($599.9 million), which is classified as a component of investments and other assets in our condensed consolidated balance sheets. In connection with the sale of Samsung Bioepis, the carrying value of our investment was reduced to zero.

For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 2, Dispositions, to these condensed consolidated financial statements.

2019 Development and Commercialization Agreement

In December 2019 we completed a transaction with Samsung Bioepis and secured the exclusive rights to commercialize two potential ophthalmology biosimilar products, BYOOVIZ (ranibizumab-nuna), a ranibizumab biosimilar referencing LUCENTIS, and SB15, a proposed aflibercept biosimilar referencing EYLEA, in major markets worldwide, including the U.S., Canada, Europe, Japan and Australia. Samsung Bioepis will be responsible for development and will supply both products to us at a pre-specified gross margin of approximately 45.0%.

In connection with this transaction, we made an upfront payment of $100.0 million to Samsung Bioepis in January 2020, of which $63.0 million was recorded as research and development expense in our condensed consolidated statements of income in 2019 and $37.0 million was recorded as intangible assets, net in our condensed consolidated balance sheets in 2019.

During the third quarter of 2021 we accrued $15.0 million in milestone payments related to the approval of BYOOVIZ in the U.S., the E.U. and the United Kingdom (U.K.), that were capitalized within intangible assets, net in our condensed consolidated balance sheets. We may also pay Samsung Bioepis up to approximately $180.0 million in additional development, regulatory and sales-based milestones.

We also acquired an option to extend the term of our 2013 commercial agreement for BENEPALI, IMRALDI and FLIXABI by an additional five years, subject to payment of an option exercise fee of $60.0 million, and obtained an option to acquire exclusive rights to commercialize these products in China.

2013 Commercial Agreement

We reflect revenue on sales of BENEPALI, IMRALDI and FLIXABI to third parties in product revenue, net in our condensed consolidated statements of income and record the related cost of revenue and sales and marketing expense in our condensed consolidated statements of income to their respective line items when these costs are incurred.

We share 50.0% of the profit or loss related to our commercial agreement with Samsung Bioepis, which is recognized in collaboration profit (loss) sharing in our condensed consolidated statements of income. For the three and nine months ended September 30, 2022, we recognized net profit-sharing expense of $48.7 million and $171.4 million, respectively, to reflect Samsung Bioepis' 50.0% sharing of the net collaboration profits, compared to a net profit-sharing expense of $71.8 million and $210.2 million, respectively, in the prior year comparative periods.

Other Services

Simultaneous with the formation of Samsung Bioepis, we also entered into a technical development services agreement, a manufacturing agreement and a license agreement with Samsung Bioepis. Revenue related to these services is reflected in revenue from collaborative and other relationships as a component of other revenue in our condensed consolidated statements of income.

Amounts receivable from Samsung Bioepis related to the agreements discussed above were $1.8 million and $4.1 million as of September 30, 2022 and December 31, 2021, respectively. Amounts payable to Samsung Bioepis related to the agreements discussed above were $53.8 million and $148.7 million as of September 30, 2022 and December 31, 2021, respectively.

For additional information on our collaboration arrangements with Samsung Bioepis and our other significant collaboration arrangements, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2021 Form 10-K.

Investments in Variable Interest Entities	9 Months Ended
Investments in Variable Interest Entities	Sep. 30, 2022
Investments in Variable Interest Entities [Abstract]
Investments in Variable Interest Entities	Consolidated Variable Interest Entities Our condensed consolidated financial statements include the financial results of variable interest entities in which we are the primary beneficiary. The following are our significant variable interest entities. Neurimmune SubOne AG We have a collaboration and license agreement with Neurimmune for the development and commercialization of antibodies for the potential treatment of Alzheimer's disease, including ADUHELM (as amended, the Neurimmune Agreement). We are responsible for the development, manufacturing and commercialization of all collaboration products. The Neurimmune Agreement is effective for the longer of the duration of certain patents relating to a licensed product or 12 years from the first commercial sale of a licensed product. We consolidate the results of Neurimmune as we determined that we are the primary beneficiary of Neurimmune because we have the power through the collaboration to direct the activities that most significantly impact the entity’s economic performance and we are required to fund 100.0% of the research and development costs incurred in support of the collaboration. In June 2021 ADUHELM was granted accelerated approval by the FDA. Under the terms of the Neurimmune Agreement, we were required to pay Neurimmune a milestone payment of $100.0 million related to the launch of ADUHELM in the U.S. During the second quarter of 2021 we made this $100.0 million payment, which was recognized as a charge to net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income. In addition, during the second quarter of 2021 we recognized net profit-sharing income of $45.0 million to reflect Eisai's 45.0% share of the $100.0 million milestone payment, which was recognized in collaboration profit (loss) sharing in our condensed consolidated statements of income. During the second quarter of 2021 we recorded a net deferred tax asset in Switzerland of approximately $490.0 million on Neurimmune's tax basis in ADUHELM, the realization of which is dependent on future sales of ADUHELM. During the fourth quarter of 2021, due to reduced future expected revenue associated with ADUHELM, we recorded a valuation allowance of approximately $390.0 million related to this deferred tax asset. During the first quarter of 2022, upon issuance of the final NCD related to ADUHELM, we recorded an additional valuation allowance of approximately $85.0 million to reduce the net value of this deferred tax asset to zero. These adjustments to our deferred tax assets and their valuation allowances are each recorded with an equal and offsetting amount assigned to net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income, resulting in a zero net impact to net income attributable to Biogen Inc. Excluding the impact of the Neurimmune deferred tax asset, the assets and liabilities of Neurimmune are not significant to our condensed consolidated financial position or results of operations as it is a research and development organization. We have provided no financing to Neurimmune other than contractually required amounts. For additional information on our collaboration arrangements with Eisai, please read Note 18, Collaborative and Other Relationships, to these condensed consolidated financial statements. Unconsolidated Variable Interest Entities We have relationships with various variable interest entities that we do not consolidate as we lack the power to direct the activities that significantly impact the economic success of these entities. These relationships include investments in certain biotechnology companies and research collaboration agreements. As of September 30, 2022 and December 31, 2021, the carrying value of our investments in certain biotechnology companies representing potential unconsolidated variable interest entities totaled $25.3 million and $24.6 million, respectively. Our maximum exposure to loss related to these variable interest entities is limited to the carrying value of our investments. We have also entered into research collaboration agreements with certain variable interest entities where we are required to fund certain development activities. These development activities are included in research and development expense in our condensed consolidated statements of income as they are incurred. We have provided no financing to these variable interest entities other than previous contractually required amounts. For additional information on our investments in Neurimmune and other variable interest entities, please read Note 19, Investments in Variable Interest Entities, to our consolidated financial statements included in our 2021 Form 10-K.

Litigation	9 Months Ended
Litigation	Sep. 30, 2022
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation	We are currently involved in various claims and legal proceedings, including the matters described below. For information as to our accounting policies relating to claims and legal proceedings, including use of estimates and contingencies, please read Note 1, Summary of Significant Accounting Policies, to our consolidated financial statements included in our 2021 Form 10-K. With respect to some loss contingencies, an estimate of the possible loss or range of loss cannot be made until management has further information, including, for example, (i) which claims, if any, will survive dispositive motion practice; (ii) information to be obtained through discovery; (iii) information as to the parties' damages claims and supporting evidence; (iv) the parties’ legal theories; and (v) the parties' settlement positions. The claims and legal proceedings in which we are involved also include challenges to the scope, validity or enforceability of the patents relating to our products, pipeline or processes and challenges to the scope, validity or enforceability of the patents held by others. These include claims by third parties that we infringe their patents. An adverse outcome in any of these proceedings could result in one or more of the following and have a material impact on our business or consolidated results of operations and financial position: (i) loss of patent protection; (ii) inability to continue to engage in certain activities; and (iii) payment of significant damages, royalties, penalties and/or license fees to third parties. Loss Contingencies ADUHELM Securities Litigation We and certain current and former officers are named as defendants in actions filed by shareholders in November 2020 (the November 2020 Securities Action) and February 2022 (the February 2022 Securities Action) and pending in the U.S. District Court for the District of Massachusetts. The actions allege violations of federal securities laws under 15 U.S.C §78j(b) and §78t(a) and 17 C.F.R. §240.10b-5 and seek declarations of the actions as class actions and monetary relief. In September 2022, the court dismissed the November 2020 Securities Action, and the plaintiff has appealed to the U.S. Court of Appeals for the First Circuit. Our motion to dismiss the February 2022 Securities Action is pending. An estimate of the possible loss or range of loss cannot be made at this time. Derivative Action We and members of the Board of Directors are named as defendants in derivative actions filed by shareholders on February 9 and July 21, 2022, in the U.S. District Court for the District of Massachusetts. The actions allege violations of federal securities laws under 15 U.S.C. §78n(a) and 17 C.F.R. §240 14.a-9, breaches of fiduciary duties and waste of corporate assets, and seek declaratory and injunctive relief, monetary relief payable to Biogen, and attorneys’ fees and costs payable to the plaintiffs. The court has stayed both cases. An estimate of the possible loss or range of loss cannot be made at this time. IMRALDI Patent Litigation In September 2018 Fresenius Kabi Deutschland GmbH (Fresenius Kabi) commenced proceedings for damages and injunctive relief against Biogen France SAS in the Tribunal de Grande Instance de Paris and proceedings against Biogen GmbH in the Düsseldorf Regional Court, alleging that IMRALDI, the adalimumab biosimilar product of Samsung Bioepis that Biogen commercializes in Europe, infringes national counterparts of European Patent No. 3 148 510 (the EP '510 Patent). In June 2022 Fresenius Kabi amended both actions to assert claims under European Patent 3 145 488 (the EP ‘488 Patent), which expires in May 2035. No hearing has been set in either action. In June 2020 Fresenius Kabi commenced preliminary injunction proceedings in Denmark's Maritime and Commercial High Court alleging that IMRALDI infringes the Danish counterpart of the EP '488 Patent and a corresponding Danish utility model, DK 2020 00038 Y3. In September 2021 the Court refused Fresenius Kabi's request for a preliminary injunction, finding that the patent and utility model are invalid and not infringed. Fresenius Kabi has appealed to the High Court of Eastern Denmark, and a hearing is scheduled for January 2023. In June 2022 the Technical Boards of Appeal (TBA) of the European Patent Office (EPO) affirmed the revocation of the EP '510 Patent, which resolves all pending infringement claims under the EP '510 Patent. The EPO has scheduled a hearing on the validity of the EP '488 Patent for October 26, 2022. In July 2019 Gedeon Richter Nyrt commenced proceedings for damages and injunctive relief against Biogen GmbH in the Düsseldorf Regional Court, alleging infringement of the German counterpart of European Patent No. 3 212 667 (EP '667 Patent), which expires in October 2035. The case has been stayed pending proceedings in the EPO to invalidate the EP '667 Patent. In July 2021 the Opposition Division of the EPO revoked the EP '667 Patent. Gedeon Richter Nyrt have appealed that decision to the TBA of the EPO. No hearing has been set in that appeal. In November 2020 Gedeon Richter Nyrt commenced proceedings against Biogen GmbH in the Düsseldorf Regional Court alleging infringement of a German utility model corresponding to EP '667. The proceeding has been stayed pending the outcome of proceedings that Biogen has filed in the German Patent and Trademark Office to cancel the utility model. No hearing has been set in the cancellation proceedings. An estimate of the possible loss or range of loss in the IMRALDI patent litigation described above cannot be made at this time. Qui Tam Litigation In September 2022, without admitting any liability, we agreed to pay $900.0 million to settle previously disclosed litigation unsealed in July 2015 and filed by Michael Bawduniak on behalf of the U.S. and certain states in the U.S. District Court for the District of Massachusetts alleging violations of the federal False Claims Act and state law counterparts. In October 2022 the court dismissed the case with prejudice. Dispute with Former Convergence Shareholders In November and December 2019 Shareholder Representative Services LLC, on behalf of the former shareholders of Convergence, sent us correspondence asserting claims of $200.0 million for alleged breach of the contract under which we acquired Convergence. We dispute the claims. ERISA Class Action Litigation In September 2020 the U.S. District Court for the District of Massachusetts consolidated two cases filed against us in July and August 2020 by participants in the Biogen 401(k) Savings Plan, alleging breach of fiduciary duty under ERISA. Plaintiffs seek a declaration of the action as a class action and monetary and other relief. An estimate of the possible loss or range of loss cannot be made at this time. Humana Patient Assistance Litigation In September 2021 Humana Inc. (Humana) filed suit against us in the U.S. District Court for the District of Massachusetts, alleging damages related to our providing MS patients with free medications and making charitable contributions to non-profit organizations that assist MS patients. Humana alleges violation of the federal RICO Act and state laws and seeks statutory treble damages, attorneys' fees and costs. We filed a motion to dismiss, which is pending. An estimate of the possible loss cannot be made at this time. Other Matters Government Investigations The U.S. House of Representatives Committees on Oversight and Reform and Energy and Commerce and the Office of Inspector General of the U.S. Department of Health and Human Services have announced investigations relating to ADUHELM. The Company also received a civil investigative demand from the Federal Trade Commission (FTC) and a subpoena from the Securities and Exchange Commission seeking information relating to ADUHELM, including healthcare sites, ADUHELM’s approval and ADUHELM’s marketing. In July 2022 the FTC informed us that it had closed its investigation. TECFIDERA Patent Matters In October 2022 the U.S. Supreme Court denied our petition for writ of certiorari for review of the previously disclosed decision of the U.S. Court of Appeals for the Federal Circuit holding that the asserted claims of our U.S. Patent No. 8,399,514 (the '514 Patent) are invalid. Thereafter, we moved to dismiss our appeals from the judgments in the previously disclosed Delaware Actions, and we and Mylan Pharmaceuticals, Inc. (Mylan) agreed that the judgment in our favor in the previously reported inter partes review filed by Mylan in 2018 should be vacated. TYSABRI Patent Matters In September 2022 we filed an action in the U.S. District Court for the District of Delaware against Sandoz Inc. and Polpharma Biologics S.A. under the Biologics Price Competition and Innovation Act, 42 U.S.C. §262, seeking a declaratory judgment of patent infringement, following our receipt of Sandoz inc.'s notice of intent to commercially market a biosimilar version of TYSABRI (natalizumab). No trial date has been set. In November 2017 Swiss Pharma International AG, affiliated with the Polpharma Group, filed an action in the Commercial Court of Rome to invalidate the Italian counterpart of the European Patent No. 1 485 127 (the EP '127 Patent), which covers administration of natalizumab to treat MS and expires in February 2023. A hearing has been set for November 2022. In August 2020 Polpharma Biologics S.A. brought an action in the Polish Patent Office to revoke our Polish Patent No. 215263, which corresponds to the EP '127 Patent and expires in February 2023. The action was suspended by the Polish Patent Office in April 2021 pending examination of our amended patent claims. In June 2021 Polpharma Biologics S.A., Sandoz B.V. and Sandoz AG filed an action in the District Court of the Hague, Netherlands to invalidate the Dutch counterpart of our European Patent 2 676 967 (the EP '967 Patent), which expires in 2027 and covers methods of treatment using natalizumab (TYSABRI) and pre-treatment testing of patients. A hearing has not been scheduled. In July 2021 the EPO revoked the EP ‘967 Patent. A hearing on our appeal to the TBA of the EPO is set for December 2022. In September 2021 Polpharma Biologics S.A., Sandoz AG, Sandoz Limited and Sandoz GmbH filed an action in the English High Court to revoke the U.K. counterpart of the EP ‘967 Patent and seeking a declaration that the patent would not be infringed by the marketing of Polpharma’s proposed natalizumab biosimilar. A hearing has been set for February 2023. Annulment Proceedings in the General Court of the European Union relating to TECFIDERA Pharmaceutical Works Polpharma SA (Polpharma) and Mylan Ireland Ltd. (Mylan Ireland) each filed actions in the General Court of the European Union (Polpharma in October 2018 and Mylan Ireland in November 2020) to annul the European Medicines Agency's (EMA) decision not to validate their applications to market generic versions of TECFIDERA on the grounds that TECFIDERA benefits from regulatory data protection. On May 5, 2021, the European General Court annulled the EMA's non-validation decision with respect to Polpharma. We have appealed the decision to the European Court of Justice and the appeal is pending. The case brought by Mylan Ireland has been stayed. Product Liability and Other Legal Proceedings We are also involved in product liability claims and other legal proceedings generally incidental to our normal business activities. While the outcome of any of these proceedings cannot be accurately predicted, we do not believe the ultimate resolution of any of these existing matters would have a material adverse effect on our business or financial condition.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2022
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS

Dispositions	9 Months Ended
Dispositions	Sep. 30, 2022
Divestitures [Abstract]
Dispositions	DISPOSITIONS Sale of Joint Venture Equity Interest in Samsung Bioepis In April 2022 we completed the sale of our 49.9% equity interest in Samsung Bioepis to Samsung BioLogics Co., Ltd (Samsung BioLogics). Under the terms of this transaction, we received approximately $1.0 billion in cash at closing and expect to receive approximately $1.3 billion in cash to be deferred over two payments of approximately $812.5 million due at the first anniversary and approximately $437.5 million due at the second anniversary of the closing of this transaction. Prior to the sale, the carrying value of our investment in Samsung Bioepis totaled $581.6 million. For the nine months ended September 30, 2022, we recognized a pre-tax gain of approximately $1.5 billion related to this transaction, which was recorded in other (income) expense, net in our condensed consolidated statements of income. This pre-tax gain included reclassifications from accumulated other comprehensive income (loss) to net income of approximately $58.9 million in cumulative translation losses, partially offset by approximately $57.0 million in gains resulting from the termination of our net investment hedge. We have concluded that the divestment of Samsung Bioepis does not meet the criteria to be reported as discontinued operations in our condensed consolidated financial statements, as our decision to divest this business does not represent a strategic shift that will have a major effect on our operations and financial results. We elected the fair value option and measured the payments due to us from Samsung BioLogics at fair value. As of September 30, 2022, the estimated fair values of the first and second payments using risk-adjusted discount rates of 4.9% and 5.3%, respectively, were approximately $790.8 million and $402.8 million, respectively. These payments have been classified as level 3 measurements and are reflected in other current assets and investments and other assets, respectively, in our condensed consolidated balance sheets. For the three and nine months ended September 30, 2022, we recognized a gain of approximately $2.7 million and a loss of approximately $4.0 million to reflect the changes in fair value related to our first and second payments, respectively. These changes were recorded in other (income) expense, net in our condensed consolidated statements of income. As part of this transaction, we are also eligible to receive up to an additional $50.0 million upon the achievement of certain commercial milestones. Our policy for contingent payments of this nature is to recognize them in the period that they become realizable, which is generally the same period in which they are earned. If any payments due to us remain outstanding after the second anniversary of the closing of this transaction, we may elect to receive shares of Samsung BioLogics common stock at a 5.0% discount in lieu of a cash payment for the remaining amount due. Currently, we believe that the likelihood of Samsung BioLogics failing to make timely payments to us for the amounts due is remote. Additionally, for the nine months ended September 30, 2022, we recorded a discrete tax expense of approximately $258.3 million related to this transaction, which is reflected in income tax (benefit) expense in our condensed consolidated statements of income.

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Overview	Biogen is a global biopharmaceutical company focused on discovering, developing and delivering worldwide innovative therapies for people living with serious neurological and neurodegenerative diseases as well as related therapeutic adjacencies. We have a leading portfolio of medicines to treat multiple sclerosis (MS), have introduced the first approved treatment for spinal muscular atrophy (SMA) and developed the first and only approved treatment to address a defining pathology of Alzheimer's disease. We also commercialize biosimilars of advanced biologics and focus on advancing our pipeline in neuroscience and specialized immunology. Lastly, we are focused on accelerating our efforts in digital health to support our commercial and pipeline programs while also creating opportunities for potential digital therapeutics. We support our drug discovery and development efforts through the commitment of significant resources to discovery, research and development programs and business development opportunities. Our marketed products include TECFIDERA, VUMERITY, AVONEX, PLEGRIDY, TYSABRI and FAMPYRA for the treatment of MS; SPINRAZA for the treatment of SMA; ADUHELM for the treatment of Alzheimer's disease; and FUMADERM for the treatment of severe plaque psoriasis. We have certain business and financial rights with respect to RITUXAN for the treatment of non-Hodgkin's lymphoma, chronic lymphocytic leukemia (CLL) and other conditions; RITUXAN HYCELA for the treatment of non-Hodgkin's lymphoma and CLL; GAZYVA for the treatment of CLL and follicular lymphoma; OCREVUS for the treatment of primary progressive MS (PPMS) and relapsing MS (RMS); and other potential anti-CD20 therapies, including mosunetuzumab, pursuant to our collaboration arrangements with Genentech, Inc. (Genentech), a wholly-owned member of the Roche Group. For additional information on our collaboration arrangements with Genentech, please read Note 18, Collaborative and Other Relationships, to our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2021 (2021 Form 10-K). Our innovative drug development and commercialization activities are complemented by our biosimilar business that expands access to medicines and reduces the cost burden for healthcare systems. Through our collaboration with Samsung Bioepis Co., Ltd. (Samsung Bioepis) we market and sell BENEPALI, an etanercept biosimilar referencing ENBREL, IMRALDI, an adalimumab biosimilar referencing HUMIRA, and FLIXABI, an infliximab biosimilar referencing REMICADE, in certain countries in Europe, as well as BYOOVIZ, a ranibizumab biosimilar referencing LUCENTIS. For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 18, Collaborative and Other Relationships, to these unaudited condensed consolidated financial statements (condensed consolidated financial statements).
Basis of presentation	In the opinion of management, our condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair statement of our financial statements for interim periods in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The information included in this quarterly report on Form 10-Q should be read in conjunction with our audited consolidated financial statements and the accompanying notes included in our 2021 Form 10-K. Our accounting policies are described in the Notes to Consolidated Financial Statements in our 2021 Form 10-K and updated, as necessary, in this report. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP. The results of operations for the three and nine months ended September 30, 2022, are not necessarily indicative of the operating results for the full year or for any other subsequent interim period. We operate as one operating segment, focused on discovering, developing and delivering worldwide innovative therapies for people living with serious neurological and neurodegenerative diseases as well as related therapeutic adjacencies.
Consolidation	Our condensed consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and those of certain variable interest entities where we are the primary beneficiary. For consolidated entities where we own or are exposed to less than 100.0% of the economics, we record net income (loss) attributable to noncontrolling interests, net of tax in our condensed consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. Intercompany balances and transactions are eliminated in consolidation. In determining whether we are the primary beneficiary of a variable interest entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. We continuously assess whether we are the primary beneficiary of a variable interest entity as changes to existing relationships or future transactions may result in us consolidating or deconsolidating one or more of our collaborators or partners.
Use of estimates	The preparation of our condensed consolidated financial statements requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, equity, revenue and expense and related disclosure of contingent assets and liabilities. On an ongoing basis we evaluate our estimates, judgments and assumptions. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets, liabilities and equity and the amount of revenue and expense. Actual results may differ from these estimates. The length of time and full extent to which the COVID-19 pandemic directly or indirectly impacts our business, results of operations and financial condition, including sales, expense, reserves and allowances, the supply chain, manufacturing, clinical trials, research and development costs and employee-related costs, depends on future developments that are highly uncertain, subject to change and are difficult to predict, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat COVID-19 as well as the economic impact on local, regional, national and international customers and markets. Additionally, the ongoing geopolitical tensions related to the conflict in Ukraine, and the related sanctions and other penalties imposed, are creating substantial uncertainty in the global economy. The extent and duration of the conflict, sanctions and resulting market disruptions are highly unpredictable. We have made estimates of the impact of the COVID-19 pandemic and the ongoing geopolitical conflict within our condensed consolidated financial statements and there may be changes to those estimates in future periods.
New accounting pronouncements	From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed below, we do not believe that the adoption of recently issued standards have had or may have a material impact on our condensed consolidated financial statements or disclosures. Fair Value Measurements In June 2022 the FASB issued Accounting Standards Update (ASU) No. 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. This standard clarifies that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. This standard becomes effective for us on January 1, 2024. We elected to early adopt this standard on a prospective basis during the third quarter of 2022.

Restructuring, Business Transformation and Other Cost Saving Initiatives (Tables)

9 Months Ended

Sep. 30, 2022

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Reserve by Type of Cost

The following table summarizes the charges and spending related to our 2022 workforce reductions for the three and nine months ended September 30, 2022:


(In millions)	Total
Restructuring reserve as of December 31, 2021	$	—
Expense	27.7
Payment	(6.2)

Restructuring reserve as of March 31, 2022	21.5
Expense	60.9
Payment	(29.7)
Foreign currency and other adjustments	(0.5)
Restructuring reserve as of June 30, 2022	52.2
Expense	21.6
Payment	(32.3)
Foreign currency and other adjustments	(1.3)
Restructuring reserve as of September 30, 2022	$	40.2

Revenues (Tables)

9 Months Ended

Sep. 30, 2022

Revenue from Contract with Customer [Abstract]

Revenues by product

Revenue by product is summarized as follows:


	For the Three Months Ended September 30,
	2022						2021
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
TECFIDERA	$	92.5	$	246.5	$	339.0	$	179.2	$	319.4	$	498.6
VUMERITY(1)	127.9		9.9		137.8		120.7		0.2		120.9
Total Fumarate	220.4		256.4		476.8		299.9		319.6		619.5
AVONEX	174.8		80.3		255.1		213.2		88.1		301.3
PLEGRIDY	39.7		41.2		80.9		39.2		47.0		86.2
Total Interferon	214.5		121.5		336.0		252.4		135.1		387.5
TYSABRI	273.0		232.5		505.5		281.1		241.7		522.8
FAMPYRA	—		22.0		22.0		—		26.2		26.2
Subtotal: MS	707.9		632.4		1,340.3		833.4		722.6		1,556.0

Spinal Muscular Atrophy:
SPINRAZA	140.2		290.9		431.1		139.8		304.3		444.1

Biosimilars:
BENEPALI	—		110.2		110.2		—		120.8		120.8
IMRALDI	—		57.7		57.7		—		57.4		57.4
FLIXABI	—		19.0		19.0		—		24.6		24.6
BYOOVIZ(2)	0.7		—		0.7		—		—		—
Subtotal: Biosimilars	0.7		186.9		187.6		—		202.8		202.8

Other:
FUMADERM	—		1.5		1.5		—		2.5		2.5
ADUHELM	1.6		—		1.6		0.3		—		0.3
Total product revenue	$	850.4	$	1,111.7	$	1,962.1	$	973.5	$	1,232.2	$	2,205.7

(1) VUMERITY became commercially available in the European Union (E.U.) during the fourth quarter of 2021.

(2) BYOOVIZ launched in the United States (U.S.) in June 2022 and became commercially available during the third quarter of 2022.


	For the Nine Months Ended September 30,
	2022						2021
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
TECFIDERA	$	330.3	$	816.5	$	1,146.8	$	520.1	$	945.3	$	1,465.4
VUMERITY(1)	383.0		19.6		402.6		285.0		0.5		285.5
Total Fumarate	713.3		836.1		1,549.4		805.1		945.8		1,750.9
AVONEX	493.8		249.6		743.4		636.4		286.9		923.3
PLEGRIDY	114.2		138.2		252.4		115.2		149.9		265.1
Total Interferon	608.0		387.8		995.8		751.6		436.8		1,188.4
TYSABRI	849.4		693.1		1,542.5		854.2		696.2		1,550.4
FAMPYRA	—		73.7		73.7		—		78.8		78.8
Subtotal: MS	2,170.7		1,990.7		4,161.4		2,410.9		2,157.6		4,568.5

Spinal Muscular Atrophy:
SPINRAZA	443.3		891.4		1,334.7		437.8		1,026.6		1,464.4

Biosimilars:
BENEPALI	—		340.7		340.7		—		363.9		363.9
IMRALDI	—		172.4		172.4		—		170.9		170.9
FLIXABI	—		62.0		62.0		—		75.4		75.4
BYOOVIZ(2)	1.2		—		1.2		—		—		—
Subtotal: Biosimilars	1.2		575.1		576.3		—		610.2		610.2

Other:
FUMADERM	—		6.4		6.4		—		8.3		8.3
ADUHELM	4.5		—		4.5		2.0		—		2.0
Total product revenue	$	2,619.7	$	3,463.6	$	6,083.3	$	2,850.7	$	3,802.7	$	6,653.4

(1) VUMERITY became commercially available in the E.U. during the fourth quarter of 2021.

(2) BYOOVIZ launched in the U.S. in June 2022 and became commercially available during the third quarter of 2022.

Analysis of change In reserves

An analysis of the change in reserves for discounts and allowances is summarized as follows:


(In millions)	Discounts		Contractual Adjustments		Returns		Total
Balance, December 31, 2021	$	137.7	$	759.6	$	38.0	$	935.3
Current provisions relating to sales in current year	499.3		1,993.6		8.5		2,501.4
Adjustments relating to prior years	(2.5)		(18.4)		(7.7)		(28.6)
Payments/credits relating to sales in current year	(379.6)		(1,442.0)		—		(1,821.6)
Payments/credits relating to sales in prior years	(124.5)		(463.7)		(14.4)		(602.6)
Balance, September 30, 2022	$	130.4	$	829.1	$	24.4	$	983.9

Total reserves included in consolidated balance sheets

The total reserves above, which are included in our condensed consolidated balance sheets, are summarized as follows:


(In millions)	As of September 30, 2022		As of December 31, 2021
Reduction of accounts receivable	$	129.4	$	133.2
Component of accrued expense and other	854.5		802.1
Total revenue-related reserves	$	983.9	$	935.3

Revenues from anti-CD20 therapeutic programs

Revenue from anti-CD20 therapeutic programs is summarized in the table below. For the purposes of this footnote, we refer to RITUXAN and RITUXAN HYCELA collectively as RITUXAN.


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Biogen’s share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	$	131.1	$	145.8	$	414.2	$	498.7
OCREVUS and other revenue from anti-CD20 therapeutic programs	285.8		269.6		838.4		745.7
Total revenue from anti-CD20 therapeutic programs	$	416.9	$	415.4	$	1,252.6	$	1,244.4

Other revenues

Other revenue is summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Revenue from collaborative and other relationships:
Revenue earned under our technical development agreement, manufacturing services agreements and royalty revenue on biosimilar products with Samsung Bioepis	$	6.5	$	6.3	$	20.9	$	15.7

Other royalty and corporate revenue:
Royalty	8.8		7.7		29.7		20.3
Other corporate	114.2		143.8		242.9		314.1
Total other revenue	$	129.5	$	157.8	$	293.5	$	350.1

Inventory (Tables)

9 Months Ended

Sep. 30, 2022

Inventory Disclosure [Abstract]

Components of inventory

The components of inventory are summarized as follows:


(In millions)	As of September 30, 2022		As of December 31, 2021
Raw materials	$	394.2	$	349.6
Work in process(1)	771.0		814.0
Finished goods	209.8		187.9
Total inventory	$	1,375.0	$	1,351.5

(1) Work in process inventory as of September 30, 2022, includes approximately $118.0 million related to lecanemab.

Intangible Assets and Goodwill (Tables)

9 Months Ended

Sep. 30, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments are summarized as follows:


		As of September 30, 2022						As of December 31, 2021
(In millions)	Estimated Life	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Completed technology	4-28 years	$	7,415.0	$	(5,579.4)	$	1,835.6	$	7,413.1	$	(5,388.5)	$	2,024.6
In-process research and development	Indefinite until commercialization	109.3		—		109.3		132.7		—		132.7
Trademarks and trade names	Indefinite	64.0		—		64.0		64.0		—		64.0
Total intangible assets		$	7,588.3	$	(5,579.4)	$	2,008.9	$	7,609.8	$	(5,388.5)	$	2,221.3

Estimated future amortization for acquired intangible assets

The estimated future amortization of finite-lived intangible assets for the next five years is expected to be as follows:


(In millions)	As of September 30, 2022
2022 (remaining three months)	$	55.0
2023	215.0
2024	195.0
2025	190.0
2026	175.0
2027	165.0

Summary of roll forward of the changes in goodwill

The following table provides a roll forward of the changes in our goodwill balance:


(In millions)	As of September 30, 2022
Goodwill, December 31, 2021	$	5,761.1

Other	(19.9)
Goodwill, September 30, 2022	$	5,741.2

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Summary of assets and liabilities recorded at fair value


	Fair Value Measurements on a Recurring Basis
	As of September 30, 2022
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	3,191.8	$	—	$	3,191.8	$	—
Marketable debt securities:
Corporate debt securities	1,219.1		—		1,219.1		—
Government securities	702.0		—		702.0		—
Mortgage and other asset backed securities	174.7		—		174.7		—
Marketable equity securities	896.0		896.0		—		—
Other current assets:
Receivable from Samsung BioLogics(1)	790.8		—		—		790.8
Other assets:
Derivative contracts	195.9		—		195.9		—
Plan assets for deferred compensation	32.2		—		32.2		—
Receivable from Samsung BioLogics(1)	402.8		—		—		402.8
Total	$	7,605.3	$	896.0	$	5,515.7	$	1,193.6
Liabilities:
Derivative contracts	$	22.8	$	—	$	22.8	$	—
Contingent consideration obligations	195.4		—		—		195.4
Total	$	218.2	$	—	$	22.8	$	195.4


	Fair Value Measurements on a Recurring Basis
	As of December 31, 2021
(In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,632.2	$	—	$	1,632.2	$	—
Marketable debt securities:
Corporate debt securities	1,108.2		—		1,108.2		—
Government securities	1,192.7		—		1,192.7		—
Mortgage and other asset backed securities	132.2		—		132.2		—
Marketable equity securities	1,048.5		181.7		866.8		—
Derivative contracts	80.9		—		80.9		—
Plan assets for deferred compensation	33.4		—		33.4		—
Total	$	5,228.1	$	181.7	$	5,046.4	$	—
Liabilities:
Derivative contracts	$	10.8	$	—	$	10.8	$	—
Contingent consideration obligations	209.1		—		—		209.1
Total	$	219.9	$	—	$	10.8	$	209.1

Summary of fair and carrying value of debt instruments

Quantitative Information about Level 3 Fair Value Measurements

Fair Value

Weighted Average

(In millions)

September 30, 2022

December 31, 2021

Valuation Technique

Significant
Unobservable Input(s)

Range

September 30, 2022

December 31, 2021

Liabilities:

Contingent consideration obligations

195.4

209.1

Discounted cash flow

Discount rate

4.50%

4.50

1.30

Expected timing of achievement of development milestones

2023 to 2028

—

The fair and carrying values of our debt instruments, which are Level 2 liabilities, are summarized as follows:


	As of September 30, 2022				As of December 31, 2021
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value

3.625% Senior Notes due September 15, 2022(1)	$	—	$	—	$	1,020.0	$	999.1
4.050% Senior Notes due September 15, 2025	1,697.8		1,744.3		1,895.2		1,742.9
2.250% Senior Notes due May 1, 2030	1,183.0		1,492.7		1,475.9		1,492.0
5.200% Senior Notes due September 15, 2045	997.2		1,100.2		1,463.0		1,099.9
3.150% Senior Notes due May 1, 2050	965.6		1,473.6		1,457.7		1,473.2
3.250% Senior Notes due February 15, 2051	452.8		468.4		692.9		466.0
Total	$	5,296.4	$	6,279.2	$	8,004.7	$	7,273.1

Fair value of contingent consideration obligations


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Fair value, beginning of period	$	197.5	$	226.3	$	209.1	$	259.8
Changes in fair value	(2.1)		(15.6)		(13.7)		(49.1)

Fair value, end of period	$	195.4	$	210.7	$	195.4	$	210.7

Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Summary of financial assets with maturities of less than 90 days included within cash and cash equivalents

The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included in cash and cash equivalents in our condensed consolidated balance sheets:


(In millions)	As of September 30, 2022		As of December 31, 2021
Commercial paper	$	3.2	$	247.6
Overnight reverse repurchase agreements	115.5		200.0
Money market funds	3,070.6		901.6
Short-term debt securities	2.5		283.0
Total	$	3,191.8	$	1,632.2

Marketable debt and equity securities

The following tables summarize our marketable debt and equity securities, classified as available-for-sale:


	As of September 30, 2022
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Marketable debt securities
Corporate debt securities:
Current	$	833.6	$	—	$	(6.9)	$	826.7
Non-current	400.5		—		(8.1)		392.4
Government securities:
Current	412.1		0.1		(3.5)		408.7
Non-current	298.8		—		(5.5)		293.3
Mortgage and other asset backed securities:
Current	0.1		—		—		0.1
Non-current	177.6		—		(3.0)		174.6
Total marketable debt securities	$	2,122.7	$	0.1	$	(27.0)	$	2,095.8

Marketable equity securities

Marketable equity securities, non-current	$	1,133.8	$	—	$	(237.8)	$	896.0
Total marketable equity securities	$	1,133.8	$	—	$	(237.8)	$	896.0


	As of December 31, 2021
(In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Marketable debt securities
Corporate debt securities:
Current	$	723.6	$	0.1	$	(0.3)	$	723.4
Non-current	385.4		0.2		(0.8)		384.8
Government securities:
Current	817.0		—		(0.4)		816.6
Non-current	377.0		0.1		(1.0)		376.1
Mortgage and other asset backed securities:
Current	1.1		—		—		1.1
Non-current	131.8		—		(0.7)		131.1
Total marketable debt securities	$	2,435.9	$	0.4	$	(3.2)	$	2,433.1

Marketable equity securities
Marketable equity securities, current	$	33.9	$	9.9	$	—	$	43.8
Marketable equity securities, non-current	1,133.1		151.0		(279.4)		1,004.7
Total marketable equity securities	$	1,167.0	$	160.9	$	(279.4)	$	1,048.5

Summary of contractual maturities: available-for-sale securities

The estimated fair value and amortized cost of our marketable debt securities classified as available-for-sale by contractual maturity are summarized as follows:


	As of September 30, 2022				As of December 31, 2021
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,235.5	$	1,245.8	$	1,541.1	$	1,541.7
Due after one year through five years	848.3		864.0		868.2		870.2
Due after five years	12.0		12.9		23.8		24.0
Total marketable debt securities	$	2,095.8	$	2,122.7	$	2,433.1	$	2,435.9

Proceeds from marketable debt securities

The proceeds from maturities and sales of marketable debt securities and resulting realized gains and losses are summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Proceeds from maturities and sales	$	1,643.2	$	575.4	$	3,104.7	$	2,028.1
Realized gains	—		0.1		—		0.4
Realized losses	7.9		0.5		9.3		1.7

Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Foreign currency forward contracts that were entered into to hedge forecasted revenue

The notional amount of foreign currency forward contracts that were entered into to hedge forecasted revenue and operating expense is summarized as follows:


	Notional Amount
(In millions)	As of September 30, 2022		As of December 31, 2021
Euro	$	1,089.2	$	1,828.0
British pound	43.5		166.2
Swiss franc	37.8		—
Japanese yen	23.5		72.7
Canadian dollar	14.7		59.9
Total foreign currency forward contracts	$	1,208.7	$	2,126.8

Summary of the effect of cash flow derivatives designated as hedging instruments on the condensed consolidated statements of income

The following tables summarize the effect of foreign currency forward contracts designated as hedging instruments in our condensed consolidated statements of income:


For the Three Months Ended September 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2022		2021		Location	2022		2021
Revenue	$	77.7	$	(14.9)	Revenue	$	6.6	$	(0.7)
Operating expense	(0.8)		(0.3)		Operating expense	(0.1)		—

For the Nine Months Ended September 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)					Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2022		2021		Location	2022		2021
Revenue	$	143.2	$	(68.7)	Revenue	$	(0.8)	$	(4.5)
Operating expense	(3.5)		(0.3)		Operating expense	(0.4)		(0.4)

Summary of the effect of derivatives designated as net investment hedging instruments on our consolidated statement of income

The following tables summarize the effect of our net investment hedges in our condensed consolidated financial statements:


For the Three Months Ended September 30,
Net Gains/(Losses) Recognized in Other Comprehensive Income (Effective Portion) (in millions)					Net Gains/(Losses) Recognized in Other Comprehensive Income (Amounts Excluded from Effectiveness Testing) (in millions)					Net Gains/(Losses) Recognized in Net Income (Amounts Excluded from Effectiveness Testing) (in millions)
Location	2022		2021		Location	2022		2021		Location	2022		2021
Gains (losses) on net investment hedges(1)	$	—	$	24.9	Gains (losses) on net investment hedges(1)	$	—	$	—	Other (income) expense(1)	$	—	$	—

For the Nine Months Ended September 30,
Net Gains/(Losses) Recognized in Other Comprehensive Income (Effective Portion) (in millions)					Net Gains/(Losses) Recognized in Other Comprehensive Income (Amounts Excluded from Effectiveness Testing) (in millions)					Net Gains/(Losses) Recognized in Net Income (Amounts Excluded from Effectiveness Testing) (in millions)
Location	2022		2021		Location	2022		2021		Location	2022		2021
Gains (losses) on net investment hedges(1)	$	20.4	$	46.1	Gains (losses) on net investment hedges(1)	$	(3.2)	$	(1.1)	Other (income) expense(1)	$	(4.6)	$	0.1

Summary of fair value and presentation of derivatives


(In millions)	Balance Sheet Location	As of September 30, 2022		As of December 31, 2021
Cash Flow Hedging Instruments:
Asset derivative instruments	Other current assets	$	158.2	$	66.2
	Investments and other assets	5.0		5.5
Liability derivative instruments	Accrued expense and other	2.6		6.6


Net Investment Hedging Instruments:(1)
Asset derivative instruments	Other current assets	21.4		4.1






Other Derivative Instruments:
Asset derivative instruments	Other current assets	11.3		5.1
Liability derivative instruments	Accrued expense and other	20.2		4.2

Derivative Instruments, Unrealized Gain (Loss)

The pre-tax portion of the fair value of these foreign currency forward contracts that were included in accumulated other comprehensive income (loss) in total equity is summarized as follows:



(In millions)	As of September 30, 2022		As of December 31, 2021
Unrealized gains	$	146.5	$	60.8
Unrealized (losses)	(2.2)		(7.0)
Net unrealized gains (losses)	$	144.3	$	53.8

Accumulated Other Comprehensive Income (Loss) (Tables)

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following tables summarize the changes in accumulated other comprehensive income (loss), net of tax by component:


(In millions)	Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax		Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Gains (Losses) on Net Investment Hedges, Net of Tax(1)		Unrealized gains (losses) on pension benefit obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2021	$	(2.2)	$	53.8	$	25.5	$	(44.8)	$	(139.0)	$	(106.7)
Other comprehensive income (loss) before reclassifications	(26.4)		204.5		12.6		4.2		(154.5)		40.4
Amounts reclassified from accumulated other comprehensive income (loss)	7.4		(125.5)		(38.1)		—		58.9		(97.3)
Net current period other comprehensive income (loss)	(19.0)		79.0		(25.5)		4.2		(95.6)		(56.9)
Balance, September 30, 2022	$	(21.2)	$	132.8	$	—	$	(40.6)	$	(234.6)	$	(163.6)


(In millions)	Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax		Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax		Gains (Losses) on Net Investment Hedges, Net of Tax		Unrealized gains (losses) on pension benefit obligation, Net of Tax		Currency Translation Adjustments		Total
Balance, December 31, 2020	$	1.4	$	(179.0)	$	(8.5)	$	(66.3)	$	(46.6)	$	(299.0)
Other comprehensive income (loss) before reclassifications	(2.5)		143.0		35.3		3.9		(80.3)		99.4
Amounts reclassified from accumulated other comprehensive income (loss)	1.1		62.0		(0.1)		—		—		63.0
Net current period other comprehensive income (loss)	(1.4)		205.0		35.2		3.9		(80.3)		162.4
Balance, September 30, 2021	$	—	$	26.0	$	26.7	$	(62.4)	$	(126.9)	$	(136.6)

Reclassification out of Accumulated Other Comprehensive Income

The following table summarizes the amounts reclassified from accumulated other comprehensive income (loss):


(In millions)	Income Statement Location	Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)
		For the Three Months Ended September 30,				For the Nine Months Ended September 30,
		2022		2021		2022		2021
Gains (losses) on securities available for sale	Other (income) expense	$	(8.0)	$	(0.4)	$	(9.4)	$	(1.3)
	Income tax benefit (expense)	1.7		0.1		2.0		0.3

Gains (losses) on cash flow hedges	Revenue	77.7		(14.9)		143.2		(68.7)
	Operating expense	(0.8)		(0.3)		(3.5)		(0.3)
	Other (income) expense	—		—		(0.2)		0.1
	Income tax benefit (expense)	(7.8)		1.5		(14.0)		6.8

Gains (losses) on net investment hedges(1)	Other (income) expense	—		—		38.1		0.1


Currency Translation Adjustments	Other (income) expense	—		—		(58.9)		—
Total reclassifications, net of tax		$	62.8	$	(14.0)	$	97.3	$	(63.0)

Earnings per Share (Tables)

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Basic and diluted earnings per share

Basic and diluted shares outstanding used in our earnings per share calculation are calculated as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Numerator:
Net income attributable to Biogen Inc.	$	1,134.7	$	329.2	$	2,496.5	$	1,187.9
Denominator:
Weighted average number of common shares outstanding	144.4		148.0		145.8		149.9
Effect of dilutive securities:

Time-vested restricted stock units	0.3		0.4		0.3		0.2
Market stock units	—		0.1		—		0.1
Performance stock units settled in stock	0.1		0.1		0.1		0.1
Dilutive potential common shares	0.4		0.6		0.4		0.4
Shares used in calculating diluted earnings per share	144.8		148.6		146.2		150.3

Share-Based Payments (Tables)

9 Months Ended

Sep. 30, 2022

Share-based Payment Arrangement [Abstract]

Share-based compensation expense included in condensed consolidated statements of income

The following table summarizes share-based compensation expense included in our condensed consolidated statements of income:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Research and development	$	24.5	$	19.5	$	72.6	$	72.2
Selling, general and administrative	46.5		42.6		129.3		127.8

Subtotal	71.0		62.1		201.9		200.0
Capitalized share-based compensation costs	(2.0)		(1.9)		(7.1)		(6.3)
Share-based compensation expense included in total cost and expense	69.0		60.2		194.8		193.7
Income tax effect	(13.0)		(10.9)		(36.0)		(35.8)
Share-based compensation expense included in net income attributable to Biogen Inc.	$	56.0	$	49.3	$	158.8	$	157.9

Summary of share-based compensation expense associated with each of our share-based compensating programs

The following table summarizes share-based compensation expense associated with each of our share-based compensation programs:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Market stock units	$	4.0	$	9.7	$	11.4	$	35.5
Time-vested restricted stock units	48.7		38.8		150.4		121.9


Performance stock units settled in stock	10.5		4.9		22.1		14.2
Performance stock units settled in cash	5.4		4.4		7.9		13.9
Employee stock purchase plan	2.4		4.3		10.1		14.5

Subtotal	71.0		62.1		201.9		200.0
Capitalized share-based compensation costs	(2.0)		(1.9)		(7.1)		(6.3)
Share-based compensation expense included in total cost and expense	$	69.0	$	60.2	$	194.8	$	193.7

Income Taxes (Tables)

9 Months Ended

Sep. 30, 2022

Income Tax Disclosure [Abstract]

Reconciliation between the U.S. federal statutory tax rate and effective tax rate

A reconciliation between the U.S. federal statutory tax rate and our effective tax rate is summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2022		2021		2022		2021
Statutory rate	21.0	%	21.0	%	21.0	%	21.0	%
State taxes	1.9		0.3		1.1		0.9
Taxes on foreign earnings	(3.4)		(20.2)		(4.4)		(11.5)
Tax credits	(1.4)		(7.1)		(1.5)		(4.1)
Purchased intangible assets	0.1		(6.2)		0.2		(1.4)



GILTI	0.8		2.6		0.5		1.6



Sale of Samsung Bioepis	(0.8)		—		(1.9)		—
Litigation settlement agreement	(1.2)		—		3.1		—
Neurimmune tax impacts	—		(0.5)		2.8		(36.4)
International reorganization	—		—		(1.7)		—
Other	0.2		1.2		0.2		0.7
Effective tax rate	17.2	%	(8.9)	%	19.4	%	(29.2)	%

Other Consolidated Financial Statement Detail (Tables)

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Other income (expense), net

Components of other (income) expense, net, are summarized as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Gain on sale of equity interest in Samsung Bioepis(1)	$	—	$	—	$	(1,505.4)	$	—
Litigation settlement agreement	—		—		900.0		—
Interest income	(23.9)		(2.6)		(39.4)		(8.2)
Interest expense	59.9		66.3		191.8		187.3
(Gains) losses on investments, net	(101.8)		424.5		167.5		707.2
Foreign exchange (gains) losses, net	11.5		13.7		39.0		23.1
Other, net	(1.7)		1.0		25.2		4.0
Total other (income) expense, net	$	(56.0)	$	502.9	$	(221.3)	$	913.4

(

Gain (loss) on investments in equity securities

The following table summarizes our (gains) losses on investments, net that relate to our equity securities held during the following periods:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Net (gains) losses recognized on equity securities	$	(109.8)	$	424.2	$	158.1	$	705.9
Less: Net (gains) losses realized on equity securities	(0.5)		(2.7)		—		(9.3)
Net unrealized (gains) losses recognized on equity securities	$	(109.3)	$	426.9	$	158.1	$	715.2

Accrued expenses and other

Accrued expense and other consists of the following:


(In millions)	As of September 30, 2022		As of December 31, 2021
Litigation settlement agreement(1)	$	900.0	$	—
Revenue-related reserves for discounts and allowances	854.5		802.1
Collaboration expense	260.1		324.7
Royalties and licensing fees	208.6		234.7
Employee compensation and benefits	313.5		345.1


Other	769.2		828.6
Total accrued expense and other	$	3,305.9	$	2,535.2

Collaborative and Other Relationships (Tables)

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Activity Related to BAN2401 and Elenbecestat Collaboration


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total development expense incurred by the collaboration related to the advancement of lecanemab and elenbecestat	$	109.3	$	118.4	$	264.9	$	236.1
Biogen's share of lecanemab and elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income	54.7		59.2		132.5		118.0
Total sales and marketing expense incurred by the Lecanemab Collaboration	29.0		5.6		68.3		15.6
Biogen's share of lecanemab and elenbecestat sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	14.5		2.8		34.2		7.8

Summary of Activity Related to Aducanumab Collaboration

A summary of development expense, sales and marketing expense and milestone payments related to the ADUHELM Collaboration Agreement is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total ADUHELM development expense	$	34.6	$	43.7	$	116.0	$	132.8
Biogen's share of ADUHELM development expense reflected in research and development expense in our condensed consolidated statements of income	19.0		24.0		63.8		73.0
Total ADUHELM sales and marketing expense incurred by the ADUHELM Collaboration Agreement	(8.0)		154.3		127.8		391.7
Biogen's share of ADUHELM sales and marketing expense reflected in selling, general and administrative expense and collaboration profit (loss) sharing in our condensed consolidated statements of income	(3.9)		83.3		68.1		211.2
Total ADUHELM collaboration third party milestones	—		—		—		100.0
Biogen's share of reimbursement from Eisai of ADUHELM milestone payments reflected in collaboration profit (loss) sharing in our condensed consolidated statements of income	—		—		—		45.0

Summary of Activity Related to Denali Therapeutics Collaboration

A summary of development expense related to this collaboration is as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Total Denali collaboration development expense	$	19.9	$	8.5	$	58.0	$	27.2
Biogen's share of Denali development expense reflected in research and development expense in our condensed consolidated statements of income	11.4		5.1		33.5		16.3

Summary of Significant Accounting Policies (Details)	9 Months Ended
Summary of Significant Accounting Policies (Details)	Sep. 30, 2022 segment
Accounting Policies [Abstract]
Number of reportable segments	1
Interest in subsidiary (less than given percentage)	100.00%

Restructuring, Business Transformation and Other Cost Saving Initiatives - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 15.4	$ 0.0		$ 124.1	$ 0.0
Employee related costs		$ 21.6			110.2
Gain due to lease termination	$ 5.3
Accelerated depreciation expense					10.4
Other restructuring costs					$ 8.8
Minimum \| Forecast
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 130.0
Maximum \| Forecast
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 150.0

Restructuring, Business Transformation and Other Cost Saving Initiatives - Restructuring Reserve Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Restructuring Cost and Reserve [Line Items]
Expense	$ 15.4			$ 0.0	$ 124.1	$ 0.0
Foreign currency and other adjustments	(1.3)	$ (0.5)
Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, beginning	52.2	21.5	$ 0.0		0.0
Expense	21.6	60.9	27.7
Payment	(32.3)	(29.7)	(6.2)
Restructuring reserve, ending	$ 40.2	$ 52.2	$ 21.5		$ 40.2

Revenues - Revenues by product (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Product revenues	$ 2,508.5	$ 2,778.9	$ 7,629.4	$ 8,247.9
MS Product Revenues
Disaggregation of Revenue [Line Items]
Product revenues	1,340.3	1,556.0	4,161.4	4,568.5
MS Product Revenues \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	707.9	833.4	2,170.7	2,410.9
MS Product Revenues \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	632.4	722.6	1,990.7	2,157.6
Fumarate
Disaggregation of Revenue [Line Items]
Product revenues	476.8	619.5	1,549.4	1,750.9
Fumarate \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	220.4	299.9	713.3	805.1
Fumarate \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	256.4	319.6	836.1	945.8
TECFIDERA
Disaggregation of Revenue [Line Items]
Product revenues	339.0	498.6	1,146.8	1,465.4
TECFIDERA \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	92.5	179.2	330.3	520.1
TECFIDERA \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	246.5	319.4	816.5	945.3
VUMERITY
Disaggregation of Revenue [Line Items]
Product revenues	137.8	120.9	402.6	285.5
VUMERITY \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	127.9	120.7	383.0	285.0
VUMERITY \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	9.9	0.2	19.6	0.5
Interferon
Disaggregation of Revenue [Line Items]
Product revenues	336.0	387.5	995.8	1,188.4
Interferon \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	214.5	252.4	608.0	751.6
Interferon \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	121.5	135.1	387.8	436.8
AVONEX
Disaggregation of Revenue [Line Items]
Product revenues	255.1	301.3	743.4	923.3
AVONEX \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	174.8	213.2	493.8	636.4
AVONEX \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	80.3	88.1	249.6	286.9
PLEGRIDY
Disaggregation of Revenue [Line Items]
Product revenues	80.9	86.2	252.4	265.1
PLEGRIDY \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	39.7	39.2	114.2	115.2
PLEGRIDY \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	41.2	47.0	138.2	149.9
TYSABRI
Disaggregation of Revenue [Line Items]
Product revenues	505.5	522.8	1,542.5	1,550.4
TYSABRI \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	273.0	281.1	849.4	854.2
TYSABRI \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	232.5	241.7	693.1	696.2
FAMPYRA
Disaggregation of Revenue [Line Items]
Product revenues	22.0	26.2	73.7	78.8
FAMPYRA \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
FAMPYRA \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	22.0	26.2	73.7	78.8
SPINRAZA
Disaggregation of Revenue [Line Items]
Product revenues	431.1	444.1	1,334.7	1,464.4
SPINRAZA \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	140.2	139.8	443.3	437.8
SPINRAZA \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	290.9	304.3	891.4	1,026.6
Biosimilars
Disaggregation of Revenue [Line Items]
Product revenues	187.6	202.8	576.3	610.2
Biosimilars \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.7	0.0	1.2	0.0
Biosimilars \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	186.9	202.8	575.1	610.2
BENEPALI
Disaggregation of Revenue [Line Items]
Product revenues	110.2	120.8	340.7	363.9
BENEPALI \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
BENEPALI \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	110.2	120.8	340.7	363.9
IMRALDI
Disaggregation of Revenue [Line Items]
Product revenues	57.7	57.4	172.4	170.9
IMRALDI \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
IMRALDI \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	57.7	57.4	172.4	170.9
FLIXABI
Disaggregation of Revenue [Line Items]
Product revenues	19.0	24.6	62.0	75.4
FLIXABI \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
FLIXABI \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	19.0	24.6	62.0	75.4
BYOOVIZ
Disaggregation of Revenue [Line Items]
Product revenues	0.7	0.0	1.2	0.0
BYOOVIZ \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.7	0.0	1.2	0.0
BYOOVIZ \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
FUMADERM
Disaggregation of Revenue [Line Items]
Product revenues	1.5	2.5	6.4	8.3
FUMADERM \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
FUMADERM \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	1.5	2.5	6.4	8.3
ADUHELM
Disaggregation of Revenue [Line Items]
Product revenues	1.6	0.3	4.5	2.0
ADUHELM \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	1.6	0.3	4.5	2.0
ADUHELM \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
Product, net
Disaggregation of Revenue [Line Items]
Product revenues	1,962.1	2,205.7	6,083.3	6,653.4
Product, net \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	850.4	973.5	2,619.7	2,850.7
Product, net \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	$ 1,111.7	$ 1,232.2	$ 3,463.6	$ 3,802.7

Revenues Reserves for Discounts and Allowances (Details 1) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 935.3
Current Provisions Relating To Sales In Current Year	2,501.4
Adjustments Relating To Prior Years	(28.6)
Payments/Returns Relating To Sales in Current Year	(1,821.6)
Payments/Returns Relating To Sales in Prior Year	(602.6)
Ending Balance	983.9
Discounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	137.7
Current Provisions Relating To Sales In Current Year	499.3
Adjustments Relating To Prior Years	(2.5)
Payments/Returns Relating To Sales in Current Year	(379.6)
Payments/Returns Relating To Sales in Prior Year	(124.5)
Ending Balance	130.4
Contractual adjustments
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	759.6
Current Provisions Relating To Sales In Current Year	1,993.6
Adjustments Relating To Prior Years	(18.4)
Payments/Returns Relating To Sales in Current Year	(1,442.0)
Payments/Returns Relating To Sales in Prior Year	(463.7)
Ending Balance	829.1
Returns
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	38.0
Current Provisions Relating To Sales In Current Year	8.5
Adjustments Relating To Prior Years	(7.7)
Payments/Returns Relating To Sales in Current Year	0.0
Payments/Returns Relating To Sales in Prior Year	(14.4)
Ending Balance	$ 24.4

Revenues- Reserves for Discounts and Allowances (Details 2) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Total Reserves	$ 983.9	$ 935.3
Reduction of accounts receivable
Total Reserves	129.4	133.2
Component of accrued expenses and other
Total Reserves	$ 854.5	$ 802.1

Revenues - Revenues from Anti-CD20 Therapeutic Programs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues from anti-CD20 therapeutic programs	$ 2,508.5	$ 2,778.9	$ 7,629.4	$ 8,247.9
Genentech
Disaggregation of Revenue [Line Items]
Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	131.1	145.8	414.2	498.7
Other revenues from anti-CD20 therapeutic programs	285.8	269.6	838.4	745.7
Revenue from anti-CD20 therapeutic programs
Disaggregation of Revenue [Line Items]
Total revenues from anti-CD20 therapeutic programs	$ 416.9	$ 415.4	$ 1,252.6	$ 1,244.4

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
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-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Revenues - Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Revenues - Other Revenues (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,508.5	$ 2,778.9	$ 7,629.4	$ 8,247.9
Royalty
Disaggregation of Revenue [Line Items]
Total revenue	8.8	7.7	29.7	20.3
Other corporate revenues
Disaggregation of Revenue [Line Items]
Total revenue	114.2	143.8	242.9	314.1
Other
Disaggregation of Revenue [Line Items]
Total revenue	129.5	157.8	293.5	350.1
Collaborative arrangement \| ZINBRYTA
Disaggregation of Revenue [Line Items]
Total revenue	$ 6.5	$ 6.3	$ 20.9	$ 15.7

- Definition

+ References

+ Details

Revenues - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
Revenues - Narrative (Details) $ in Millions	Sep. 30, 2022 USD ($) wholesaler	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) wholesaler	Sep. 30, 2021 USD ($)
Disaggregation of Revenue [Line Items]
Other Revenues	$ 2,508.5	$ 2,778.9	$ 7,629.4	$ 8,247.9
Number of wholesalers \| wholesaler	2		2
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	26.90%	26.90%	26.80%	29.10%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	10.50%	10.80%	10.70%	10.00%
Other corporate revenues
Disaggregation of Revenue [Line Items]
Other Revenues	$ 114.2	$ 143.8	$ 242.9	$ 314.1
Other
Disaggregation of Revenue [Line Items]
Other Revenues	$ 129.5	$ 157.8	$ 293.5	$ 350.1

- Definition

+ References

+ Details

Inventory - Components of Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Inventory [Line Items]
Raw materials	$ 394.2	$ 349.6
Work in process	771.0	814.0
Finished goods	209.8	187.9
Total inventory	1,375.0	$ 1,351.5
Lecanemab
Inventory [Line Items]
Work in process	$ 118.0

Inventory - Narrative (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended
Inventory - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Inventory [Line Items]
Excess and obsolescence charges related to inventory						$ 321.6	$ 36.5
(Gain) loss on equity method investments						$ 2.6	17.2
Percentage of future development costs related to Eisai						45.00%
Eisai
Inventory [Line Items]
(Gain) loss on equity method investments	$ 3.4				$ 50.6	$ 214.0	$ 90.7
Percentage of future development costs related to Eisai					45.00%
ADUHELM
Inventory [Line Items]
Excess and obsolescence charges related to inventory		$ 275.0	$ 120.0
Inventory				$ 223.0
ADUHELM \| Eisai
Inventory [Line Items]
(Gain) loss on equity method investments			$ 59.0	$ 45.0	$ 45.0	177.0
ADUHELM \| Eisai \| Centers for Medicare and Medicaid Service
Inventory [Line Items]
(Gain) loss on equity method investments						$ 136.0

Intangible Assets and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Intangible assets
Total intangible assets, gross	$ 7,588.3		$ 7,588.3		$ 7,609.8
Accumulated Amortization	(5,579.4)		(5,579.4)		(5,388.5)
Intangible assets, net	2,008.9		2,008.9		2,221.3
Amortization and impairment of acquired intangible assets	56.5	$ 111.0	190.9	$ 813.2
Expected future amortization expense, 2019 (remaining three months)	55.0		55.0
Expected future amortization expense, 2020	215.0		215.0
Expected future amortization expense, 2021	195.0		195.0
Expected future amortization expense, 2022	190.0		190.0
Expected future amortization expense, 2023	175.0		175.0
Expected future amortization expense, 2024	165.0		165.0
Completed technology
Intangible assets
Cost	7,415.0		7,415.0		7,413.1
Net	1,835.6		1,835.6		2,024.6
Accumulated Amortization	(5,579.4)		$ (5,579.4)		(5,388.5)
Completed technology \| Minimum
Intangible assets
Useful life			4 years
Completed technology \| Maximum
Intangible assets
Useful life			28 years
In-process research and development
Intangible assets
Cost and Net	109.3		$ 109.3		132.7
Accumulated Amortization	0.0		0.0		0.0
Indefinite-lived Intangible Assets (Excluding Goodwill)	109.3		109.3		132.7
Trademarks and Trade Names
Intangible assets
Cost and Net	64.0		64.0		64.0
Accumulated Amortization	0.0		0.0		0.0
Indefinite-lived Intangible Assets (Excluding Goodwill)	64.0		64.0		$ 64.0
BIIB111
Intangible assets
Amortization and impairment of acquired intangible assets		15.0		365.0
BIIB112
Intangible assets
Amortization and impairment of acquired intangible assets		28.4		220.0
Vixotrigine
Intangible assets
Amortization and impairment of acquired intangible assets				$ 44.3
TGN \| In-process research and development
Intangible assets
Cost and Net	109.3		109.3
Indefinite-lived Intangible Assets (Excluding Goodwill)	$ 109.3		$ 109.3
BIIB111 and BIIB112
Intangible assets
Amortization and impairment of acquired intangible assets		$ 39.1

Intangible Assets and Goodwill (Details 1)	9 Months Ended
Intangible Assets and Goodwill (Details 1)	Sep. 30, 2022 USD ($)
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period	$ 5,761,100,000
Other	(19,900,000)
Goodwill, end of period	5,741,200,000
Accumulated impairment losses related to goodwill	$ 0

Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Assets:
Marketable debt securities	$ 2,095.8		$ 2,433.1
Samsung Bioepis
Liabilities:
Equity, ownership interest	49.90%
Fair Value, Measurements Recurring
Assets:
Cash equivalents	$ 3,191.8		1,632.2
Marketable equity securities	896.0		1,048.5
Derivative contracts	195.9		80.9
Plan assets for deferred compensation	32.2		33.4
Total	7,605.3		5,228.1
Liabilities:
Derivative contracts	22.8		10.8
Contingent consideration obligations	195.4	$ 197.5	209.1	$ 210.7	$ 226.3	$ 259.8
Total	218.2		219.9
Fair Value, Measurements Recurring \| Samsung Bioepis
Assets:
Other current assets, receivable	790.8
Other assets, receivable	402.8
Fair Value, Measurements Recurring \| Corporate debt securities
Assets:
Marketable debt securities	1,219.1		1,108.2
Fair Value, Measurements Recurring \| Government securities
Assets:
Marketable debt securities	702.0		1,192.7
Fair Value, Measurements Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	174.7		132.2
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements Recurring
Assets:
Cash equivalents	0.0		0.0
Marketable equity securities	896.0		181.7
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	896.0		181.7
Liabilities:
Derivative contracts	0.0		0.0
Contingent consideration obligations	0.0		0.0
Total	0.0		0.0
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements Recurring \| Samsung Bioepis
Assets:
Other current assets, receivable	0.0
Other assets, receivable	0.0
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements Recurring \| Corporate debt securities
Assets:
Marketable debt securities	0.0		0.0
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements Recurring \| Government securities
Assets:
Marketable debt securities	0.0		0.0
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	0.0		0.0
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements Recurring
Assets:
Cash equivalents	3,191.8		1,632.2
Marketable equity securities	0.0		866.8
Derivative contracts	195.9		80.9
Plan assets for deferred compensation	32.2		33.4
Total	5,515.7		5,046.4
Liabilities:
Derivative contracts	22.8		10.8
Contingent consideration obligations	0.0		0.0
Total	22.8		10.8
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements Recurring \| Samsung Bioepis
Assets:
Other current assets, receivable	0.0
Other assets, receivable	0.0
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements Recurring \| Corporate debt securities
Assets:
Marketable debt securities	1,219.1		1,108.2
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements Recurring \| Government securities
Assets:
Marketable debt securities	702.0		1,192.7
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	174.7		132.2
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements Recurring
Assets:
Cash equivalents	0.0		0.0
Marketable equity securities	0.0		0.0
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	1,193.6		0.0
Liabilities:
Derivative contracts	0.0		0.0
Contingent consideration obligations	195.4		209.1
Total	195.4		209.1
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements Recurring \| Samsung Bioepis
Assets:
Other current assets, receivable	790.8
Other assets, receivable	402.8
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements Recurring \| Corporate debt securities
Assets:
Marketable debt securities	0.0		0.0
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements Recurring \| Government securities
Assets:
Marketable debt securities	0.0		0.0
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	$ 0.0		$ 0.0

Fair Value Measurements (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
Fair Value Measurements (Details Textual) - USD ($)	Sep. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Asset impairment charges	$ 0	$ 0
Contingent consideration obligations	$ 195,400,000	$ 195,400,000	$ 209,100,000
Technological and Regulatory Success, Probability		10.90%

Fair Value Measurements Fair Value Measurements - Contingent Consideration (Details) - Discount rate	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.0450
December 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.0450	0.0130

Fair Value Measurements (Details 1) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Notes payable, carrying value	$ 6,279.2	$ 7,273.1
Debt instruments, fair value	$ 5,296.4	8,004.7
Senior notes interest rate	3.625%
3.625% Senior Notes due 2022
Debt Instrument [Line Items]
Notes payable, fair value	$ 0.0	1,020.0
Notes payable, carrying value	$ 0.0	999.1
Senior notes interest rate	3.625%
4.050% Senior Notes due 2025
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,697.8	1,895.2
Notes payable, carrying value	$ 1,744.3	1,742.9
Senior notes interest rate	4.05%
2.250% Senior Notes due May 1, 2030
Debt Instrument [Line Items]
Notes payable, fair value	$ 997.2	1,475.9
Notes payable, carrying value	$ 1,100.2	1,492.0
Senior notes interest rate	2.25%
5.200% Senior Notes due 2045
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,183.0	1,463.0
Notes payable, carrying value	$ 1,492.7	1,099.9
Senior notes interest rate	5.20%
3.150% Senior Notes due May 1, 2050
Debt Instrument [Line Items]
Notes payable, fair value	$ 965.6	1,457.7
Notes payable, carrying value	$ 1,473.6	1,473.2
Senior notes interest rate	3.15%
3.250% Senior Notes, Due February 15, 2051
Debt Instrument [Line Items]
Notes payable, fair value	$ 452.8	692.9
Notes payable, carrying value	$ 468.4	$ 466.0
Senior notes interest rate	3.25%

Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Fair Value Measurements (Details 2) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration impairment	$ 2.1	$ 15.6	$ 13.7	$ 49.1
Fair Value, Measurements Recurring
Business Acquisition, Contingent Consideration [Line Items]
Fair value, beginning of period	197.5	226.3	209.1	259.8
Fair value, end of period	$ 195.4	$ 210.7	$ 195.4	$ 210.7

Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 3,191.8	$ 1,632.2
Commercial paper
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	3.2	247.6
Overnight reverse repurchase agreements
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	115.5	200.0
Money market funds
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	3,070.6	901.6
Short-term debt securities
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 2.5	$ 283.0

Financial Instruments (Details 1) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Marketable debt securities
Amortized Cost	$ 2,122.7	$ 2,435.9
Gross unrealized gains	0.1	0.4
Gross unrealized losses	(27.0)	(3.2)
Fair value	2,095.8	2,433.1
Marketable equity securities
Amortized Cost	1,133.8	1,167.0
Gross Unrealized Gains	0.0	160.9
Gross Unrealized Losses	(237.8)	(279.4)
Fair Value	896.0	1,048.5
Corporate debt securities Current
Marketable debt securities
Amortized Cost	833.6	723.6
Gross unrealized gains	0.0	0.1
Gross unrealized losses	(6.9)	(0.3)
Fair value	826.7	723.4
Corporate debt securities Non-current
Marketable debt securities
Amortized Cost	400.5	385.4
Gross unrealized gains	0.0	0.2
Gross unrealized losses	(8.1)	(0.8)
Fair value	392.4	384.8
Government securities Current
Marketable debt securities
Amortized Cost	412.1	817.0
Gross unrealized gains	0.1	0.0
Gross unrealized losses	(3.5)	(0.4)
Fair value	408.7	816.6
Government securities Non-current
Marketable debt securities
Amortized Cost	298.8	377.0
Gross unrealized gains	0.0	0.1
Gross unrealized losses	(5.5)	(1.0)
Fair value	293.3	376.1
Mortgage and other asset backed securities Current
Marketable debt securities
Amortized Cost	0.1	1.1
Gross unrealized gains	0.0	0.0
Gross unrealized losses	0.0	0.0
Fair value	0.1	1.1
Mortgage and other asset backed securities Non-current
Marketable debt securities
Amortized Cost	177.6	131.8
Gross unrealized gains	0.0	0.0
Gross unrealized losses	(3.0)	(0.7)
Fair value	174.6	131.1
Equity Securities, Current
Marketable equity securities
Amortized Cost		33.9
Gross Unrealized Gains		9.9
Gross Unrealized Losses		0.0
Fair Value		43.8
Equity Securities, Non-Current
Marketable equity securities
Amortized Cost	1,133.8	1,133.1
Gross Unrealized Gains	0.0	151.0
Gross Unrealized Losses	(237.8)	(279.4)
Fair Value	$ 896.0	$ 1,004.7

Financial Instruments (Details 2) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Summary of Contractual Maturities: Available-for-Sale Securities
Due in one year or less, amortized cost	$ 1,235.5	$ 1,541.1
Due in one year or less, estimated fair value	1,245.8	1,541.7
Due after one year through five years, amortized cost	848.3	868.2
Due after one year through five years, estimated fair value	864.0	870.2
Due after five years, amortized cost	12.0	23.8
Due after five years, estimated fair value	12.9	24.0
Estimated Fair Value	2,095.8	2,433.1
Amortized Cost	$ 2,122.7	$ 2,435.9

Financial Instruments (Details 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Financial Instruments (Details 3) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Proceeds from maturities and sales	$ 1,643.2	$ 575.4	$ 3,104.7	$ 2,028.1
Realized gains	0.0	0.1	0.0	0.4
Realized losses	$ 7.9	$ 0.5	$ 9.3	$ 1.7

Financial Instruments (Details Textual)	3 Months Ended	9 Months Ended
Financial Instruments (Details Textual)	Mar. 31, 2022	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Average maturity of marketable securities, months	10 months	9 months

Financial Instruments Financial Instruments (Details Textual 2) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Other noncurrent assets \| Strategic Investments
Business Acquisition [Line Items]
Strategic investment portfolio	$ 948.5	$ 1,110.3

Derivative Instruments (Details) $ in Millions, ₩ in Billions	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	Nov. 30, 2018 USD ($)	Nov. 30, 2018 KRW (₩)	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	May 31, 2018
Derivatives [Line Items]
Gain (loss) on foreign currency derivative instruments not designated as hedging instruments			$ 36.5		$ (13.5)	$ 85.8	$ (26.1)
Gains (losses) on net investment hedges, net of tax			0.0		15.1	$ (25.5)	35.2
Minimum
Derivatives [Line Items]
Range of durations of foreign currency forward contracts								1 month
Maximum
Derivatives [Line Items]
Range of durations of foreign currency forward contracts						15 months		15 months
Not designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			1,285.4			$ 1,285.4		$ 1,268.0
Other current assets \| Designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			158.2			158.2		66.2
Other current assets \| Not designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			11.3			11.3		5.1
Other noncurrent assets \| Designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			5.0			5.0		5.5
Accrued expenses and other \| Designated as hedging instrument
Derivatives [Line Items]
Derivative liability, fair value			2.6			2.6		6.6
Accrued expenses and other \| Not designated as hedging instrument
Derivatives [Line Items]
Derivative liability, fair value			20.2			20.2		4.2
Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			1,208.7			1,208.7		2,126.8
Foreign Exchange Forward
Derivatives [Line Items]
Unrealized Gain on Derivatives						146.5	60.8
Unrealized Loss on Derivatives						(2.2)	(7.0)
Unrealized Gain (Loss) on Derivatives						144.3	53.8
Net Investment Hedging
Derivatives [Line Items]
Unrealized gain (loss) on net investment hedges in AOCI				$ 10.6
Derivative qualifying as net investment hedge, excluded component								3.6
Gains (losses) on net investment hedges, net of tax			0.0		24.9	20.4	46.1
Gains (losses) on net investment hedge, excluded component			0.0		0.0	(3.2)	(1.1)
Net Investment Hedging \| Foreign exchange contract \| Other current assets
Derivatives [Line Items]
Derivative asset, fair value			21.4			21.4		4.1
Revenue \| Foreign exchange contract
Derivatives [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax			77.7		(14.9)	143.2	(68.7)
Revenue \| Cash flows, revenue \| Foreign exchange contract
Derivatives [Line Items]
Gain on interest rate swap			6.6		(0.7)	(0.8)	(4.5)
Operating expense \| Foreign exchange contract
Derivatives [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax			(0.8)		(0.3)	(3.5)	(0.3)
Operating expense \| Cash flows, operating expenses \| Foreign exchange contract
Derivatives [Line Items]
Gain on interest rate swap			(0.1)		0.0	(0.4)	(0.4)
Other income (expense) \| Net Investment Hedging
Derivatives [Line Items]
Gain (loss) recognized in net income, excluded component			0.0		$ 0.0	(4.6)	$ 0.1
Euro \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			1,089.2			1,089.2		1,828.0
British pound \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			23.5			23.5		72.7
Swiss franc \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			43.5			43.5		166.2
Japan, Yen \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			14.7			14.7		59.9
Canadian dollar \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			$ 37.8			$ 37.8		$ 0.0
Samsung Bioepis
Derivatives [Line Items]
Equity, ownership interest			49.90%			49.90%
Percentage of stake in entity									5.00%
Payments to acquire additional investment in equity method investment	$ 676.6	₩ 759.5
Short-term derivative
Derivatives [Line Items]
Range of durations of foreign currency forward contracts						12 months
Gain/Loss on fair value of foreign currency forward contracts			$ 142.6			$ 142.6

Property, Plant and Equipment (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
Property, Plant and Equipment (Details) $ in Millions	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) ft²	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 2,098.0	$ 2,098.0		$ 2,098.0		$ 2,006.6
Depreciation		64.2	$ 65.1	207.7	$ 168.7
Sales price				582.6	0.0
Gain on sale of building		503.7	$ 0.0	503.7	$ 0.0
Property, plant and equipment, net	3,266.4	3,266.4		3,266.4		3,416.4
125 Broadway Building
Property, Plant and Equipment [Line Items]
Sales price	603.0
Tenant allowance				10.8
Gain on sale of building	503.7
Property, plant and equipment, net	79.2	79.2		79.2
Building \| 125 Broadway Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	72.6	72.6		72.6
Land \| 125 Broadway Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	1.6	1.6		1.6
Machinery and Equipment \| 125 Broadway Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	5.0	5.0		$ 5.0
Biologics Manufacturing
Property, Plant and Equipment [Line Items]
Number of square feet \| ft²				393,000
Warehouse, Utilities and Support Space
Property, Plant and Equipment [Line Items]
Number of square feet \| ft²				290,000
Administrative Space
Property, Plant and Equipment [Line Items]
Number of square feet \| ft²				51,000
Solothurn, Switzerland
Property, Plant and Equipment [Line Items]
Construction in progress	701.0	701.0		$ 701.0		$ 677.0
Fixed assets placed into service	$ 1,200.0	$ 1,200.0		$ 1,200.0

Leases (Details Textual) - USD ($) $ in Millions	1 Months Ended
Leases (Details Textual) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Operating Leased Assets [Line Items]
Operating lease assets	$ 424.5	$ 375.4
Right-of-use assets derecognized	47.4
Lease liabilities derecognized	52.7
Gain due to lease termination	$ 5.3
125 Broadway Building
Operating Leased Assets [Line Items]
Lease term	5 years 6 months
Operating lease assets	$ 168.2
Operating lease liabilities	$ 168.2

Indebtedness (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
Indebtedness (Details) - USD ($) $ in Millions	Jul. 31, 2022	Feb. 28, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 15, 2022	Sep. 15, 2015
Debt Instrument [Line Items]
Face amount								$ 1,000.0
Redemption rate							99.92%
Senior notes interest rate			3.625%		3.625%
Extinguishment of Debt, Amount	$ 2.4
Repayments of Senior Debt		$ 151.8
Interest Expense			$ 59.9	$ 66.3	$ 191.8	$ 187.3
5.200% Senior Notes due 2045
Debt Instrument [Line Items]
Senior notes interest rate			5.20%		5.20%
Repayments of Senior Debt		12.1
Debt Instrument, Redemption, Amount		8.9
Long Term Debt, Exchanged, Amount		624.6
Gain (Loss) on Extinguishment of Debt			$ 3.2
Repayments of borrowings and premiums paid on debt exchange			13.8
Interest Expense			$ 6.1
3.250% Senior Notes, Due February 15, 2051
Debt Instrument [Line Items]
Senior notes interest rate			3.25%		3.25%
Long Term Debt, Exchanged, Amount		$ 700.7

Share Repurchases (Details) - USD ($) shares in Millions	3 Months Ended	9 Months Ended
Share Repurchases (Details) - USD ($) shares in Millions	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Oct. 31, 2020
Class of Stock [Line Items]
Payments for repurchase of common stock		$ 750,000,000.0	$ 1,800,000,000
2020 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 5,000,000,000
Repurchase of common stock, at cost, shares	2.2		6.0
Payments for repurchase of common stock	$ 750,000,000		$ 1,800,000,000
Amount remaining under 2019 Share Repurchase Program		$ 2,100,000,000

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			$ (106.7)	$ (299.0)
Balance, January 1, 2018	$ (163.6)	$ (136.6)	(163.6)	(136.6)
Other comprehensive income (loss), before reclassifications, net of tax			40.4	99.4
Amounts reclassified from accumulated other comprehensive income, net of tax			(97.3)	63.0
Other comprehensive income (loss), net of tax	(53.2)	35.2	(56.9)	163.0
Accumulated other comprehensive income (loss), net of tax ending balance	(163.6)	(136.6)	(163.6)	(136.6)
Other comprehensive income (loss), net of tax	(53.2)	35.2	(56.9)	162.4
Unrealized gains (losses) on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			(2.2)	1.4
Balance, January 1, 2018	(21.2)	0.0	(21.2)	0.0
Other comprehensive income (loss), before reclassifications, net of tax			(26.4)	(2.5)
Amounts reclassified from accumulated other comprehensive income, net of tax			7.4	1.1
Other comprehensive income (loss), net of tax			(19.0)	(1.4)
Accumulated other comprehensive income (loss), net of tax ending balance	(21.2)	0.0	(21.2)	0.0
Unrealized gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			53.8	(179.0)
Balance, January 1, 2018	132.8	26.0	132.8	26.0
Other comprehensive income (loss), before reclassifications, net of tax			204.5	143.0
Amounts reclassified from accumulated other comprehensive income, net of tax			(125.5)	62.0
Other comprehensive income (loss), net of tax			79.0	205.0
Accumulated other comprehensive income (loss), net of tax ending balance	132.8	26.0	132.8	26.0
Gains (losses) on net investment hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			25.5	(8.5)
Balance, January 1, 2018	0.0	26.7	0.0	26.7
Other comprehensive income (loss), before reclassifications, net of tax			12.6	35.3
Amounts reclassified from accumulated other comprehensive income, net of tax			(38.1)	(0.1)
Other comprehensive income (loss), net of tax			(25.5)	35.2
Accumulated other comprehensive income (loss), net of tax ending balance	0.0	26.7	0.0	26.7
Unfunded status of postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			(44.8)	(66.3)
Balance, January 1, 2018	(40.6)	(62.4)	(40.6)	(62.4)
Other comprehensive income (loss), before reclassifications, net of tax			4.2	3.9
Amounts reclassified from accumulated other comprehensive income, net of tax			0.0	0.0
Other comprehensive income (loss), net of tax			4.2	3.9
Accumulated other comprehensive income (loss), net of tax ending balance	(40.6)	(62.4)	(40.6)	(62.4)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			(139.0)	(46.6)
Balance, January 1, 2018	(234.6)	(126.9)	(234.6)	(126.9)
Other comprehensive income (loss), before reclassifications, net of tax			(154.5)	(80.3)
Amounts reclassified from accumulated other comprehensive income, net of tax			58.9	0.0
Other comprehensive income (loss), net of tax			(95.6)	(80.3)
Accumulated other comprehensive income (loss), net of tax ending balance	$ (234.6)	$ (126.9)	$ (234.6)	$ (126.9)

Reclassification out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other (income) expense	$ 56.0	$ (502.9)	$ 221.3	$ (913.4)
Income Tax Expense (Benefit)	236.2	(25.9)	578.5	(390.7)
Product revenues	2,508.5	2,778.9	7,629.4	8,247.9
Net income attributable to Biogen Inc.	$ 1,134.7	329.2	$ 2,496.5	1,187.9
Samsung Bioepis
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Equity, ownership interest	49.90%		49.90%
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income attributable to Biogen Inc.	$ 62.8	(14.0)	$ 97.3	(63.0)
Unrealized gains (losses) on securities available for sale \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other (income) expense	(8.0)	(0.4)	(9.4)	(1.3)
Income Tax Expense (Benefit)	1.7	0.1	2.0	0.3
Unrealized gains (losses) on cash flow hedges \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other (income) expense	0.0	0.0	(0.2)	0.1
Income Tax Expense (Benefit)	(7.8)	1.5	(14.0)	6.8
Product revenues	77.7	(14.9)	143.2	(68.7)
Operating Expenses	(0.8)	(0.3)	(3.5)	(0.3)
Gains (losses) on net investment hedge \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other (income) expense	0.0	0.0	38.1	0.1
Currency Translation Adjustments \| Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other (income) expense	$ 0.0	$ 0.0	$ (58.9)	$ 0.0

Earnings per Share (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net income attributable to Biogen Inc.	$ 1,134.7	$ 329.2	$ 2,496.5	$ 1,187.9
Weighted-average shares used in calculating:
Weighted average number of common shares outstanding	144,400	148,000	145,800	149,900
Effect of dilutive securities:
Dilutive potential common shares	400	600	400	400
Shares used in calculating diluted earnings per share	144,800	148,600	146,200	150,300
Time-vested restricted stock units
Effect of dilutive securities:
Stock units	300	400	300	200
Market stock units
Effect of dilutive securities:
Stock units	0	100	0	100
Performance stock units settled in stock
Effect of dilutive securities:
Stock units	100	100	100	100

Share-Based Payments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Share-Based Payments (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	$ (65.7)	$ (57.6)	$ (194.1)	$ (186.1)
Subtotal	71.0	62.1	201.9	200.0
Capitalized share-based compensation costs	(2.0)	(1.9)	(7.1)	(6.3)
Share-based compensation expense included in total costs and expenses	69.0	60.2	194.8	193.7
Income tax effect	(13.0)	(10.9)	(36.0)	(35.8)
Research and development
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	24.5	19.5	72.6	72.2
Selling, general and administrative
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	46.5	42.6	129.3	127.8
Total share-based compensation expense, net of tax
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	$ 56.0	$ 49.3	$ 158.8	$ 157.9

Share-Based Payments (Details 1) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Share-Based Payments (Details 1) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	$ (65.7)	$ (57.6)	$ (194.1)	$ (186.1)
Subtotal	71.0	62.1	201.9	200.0
Capitalized share-based compensation costs	(2.0)	(1.9)	(7.1)	(6.3)
Share-based compensation expense included in total costs and expenses	69.0	60.2	194.8	193.7
Market stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	4.0	9.7	11.4	35.5
Time-vested restricted stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	48.7	38.8	150.4	121.9
Performance stock units settled in stock
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	10.5	4.9	22.1	14.2
Performance stock units settled in cash
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	5.4	4.4	7.9	13.9
Employee stock purchase plan
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	$ 2.4	$ 4.3	$ 10.1	$ 14.5

Income Taxes (Details Textual) $ in Millions, ₩ in Billions	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 KRW (₩)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 KRW (₩)
Income Tax Contingency [Line Items]
Deferred tax assets, unrecognized tax benefit		$ 85.0		$ 390.0
Deferred tax assets, net				490.0
Samsung Bioepis
Income Tax Contingency [Line Items]
Investment in Samsung Bioepis			₩ 0.0	$ 599.9	₩ 713.3
Forecast
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	$ 500.0
Forecast \| ADUHELM
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	$ 455.0

Income Taxes (Details)	3 Months Ended		9 Months Ended
Income Taxes (Details)	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reconciliation between the U.S. federal statutory tax rate and effective tax rate
Statutory rate	21.00%	21.00%	21.00%	21.00%
State taxes	1.90%	0.30%	1.10%	0.90%
Taxes on foreign earnings	(3.40%)	(20.20%)	(4.40%)	(11.50%)
Credits and net operating loss utilization	(1.40%)	(7.10%)	(1.50%)	(4.10%)
Purchased intangible assets	0.10%	(6.20%)	0.20%	(1.40%)
GILTI	0.80%	2.60%	0.50%	1.60%
Sale of Samsung Bioepis	(0.80%)	0.00%	(1.90%)	0.00%
Litigation settlement agreement	(1.20%)	0.00%	3.10%	0.00%
Neurimmune tax impacts	0	(0.005)	0.028	(0.364)
International reorganization	0.00%	0.00%	(1.70%)	0.00%
Other	0.20%	1.20%	0.20%	0.70%
Effective tax rate	17.20%	(8.90%)	19.40%	(29.20%)

Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Other Income (Expense), Net
Gain on sale of equity interest in Samsung Bioepis(1)	$ 0.0		$ 0.0	$ (1,505.4)	$ 0.0
Litigation settlement agreement	0.0	$ 900.0	0.0	900.0	0.0
Interest income	(23.9)		(2.6)	(39.4)	(8.2)
Interest expense	59.9		66.3	191.8	187.3
(Gains) losses on investments, net	(101.8)		424.5	167.5	707.2
Foreign exchange (gains) losses, net	11.5		13.7	39.0	23.1
Other, net	(1.7)		1.0	25.2	4.0
Other (income) expense	(56.0)		502.9	(221.3)	913.4
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net (gains) losses recognized on equity securities	(109.8)		424.2	158.1	705.9
Less: Net (gains) losses realized on equity securities	(0.5)		(2.7)	0.0	(9.3)
Net unrealized (gains) losses recognized on equity securities	(109.3)		$ 426.9	158.1	$ 715.2
Accrued Expenses and Other
Litigation settlement agreement(1)	900.0			900.0		$ 0.0
Revenue-related reserves for discounts and allowances	983.9			983.9		935.3
Collaboration expense	313.5			313.5		345.1
Royalties and licensing fees	208.6			208.6		234.7
Collaboration expense	260.1			260.1		324.7
Other	769.2			769.2		828.6
Total accrued expense and other	3,305.9			3,305.9		2,535.2
Ionis, Sangamo, Denali and Sage
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net unrealized (gains) losses recognized on equity securities	112.5			198.0
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 854.5			$ 854.5		$ 802.1

Other Consolidated Financial Statement (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Net gains recognized on the increase in fair value of equity securities	$ (109.3)	$ 426.9	$ 158.1	$ 715.2
Net gains (losses) realized during the period on equity securities	(0.5)	$ (2.7)	0.0	$ (9.3)
Other long-term liabilities	1,198.1		1,198.1		$ 1,320.5
Accrued income taxes	559.7		559.7		$ 664.5
Ionis, Sangamo, Denali and Sage
Net gains recognized on the increase in fair value of equity securities	$ 112.5		$ 198.0

Collaborative and Other Relationships - Collaborations (Details) $ in Millions	1 Months Ended				3 Months Ended					6 Months Ended		9 Months Ended
	Apr. 30, 2022 USD ($)	Aug. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2019 product	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of future development costs related to Eisai												45.00%
Research and Development Expense (Excluding Acquired in Process Cost)					$ 549.2			$ 702.4				$ 1,629.5	$ 1,801.7
Cost of sales, excluding amortization and impairment of acquired intangible assets					469.5			511.8				1,707.4	1,449.6
(Gain) loss on equity method investments												2.6	17.2
Samsung Bioepis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
(Gain) loss on equity method investments								8.9				17.0	39.5
Loss recorded on Samsung Bioepis joint venture								1.1				2.6	17.2
Amortization								$ 7.8				14.4	22.3
ADUHELM
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense												300.0
Cost of sales, excluding amortization and impairment of acquired intangible assets						$ 275.0
ADUHELM \| Maximum \| Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense										$ 335.0
Eisai
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of future development costs related to Eisai								45.00%
(Gain) loss on equity method investments					3.4			$ 50.6				214.0	90.7
Due from Related Parties					110.6		$ 285.4					110.6
Due to Related Parties					81.7		46.5					81.7
Eisai \| BAN2401 and Elenbecestat
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense Incurred By Collaboration					109.3			118.4				264.9	236.1
Expense reflected within statements of income					54.7			59.2				132.5	118.0
Eisai \| ADUHELM
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense reflected within statements of income					0.0			0.0				0.0	45.0
Additional milestone payment			$ 100.0		0.0			0.0				0.0	100.0
(Gain) loss on equity method investments						$ 59.0	45.0	45.0				$ 177.0
Samsung Bioepis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront and milestone payments made to collaborative partner									$ 100.0
Collaboration agreement term												5 years
Research and development expense									$ 63.0
Additional milestone payment	$ 50.0
Due from Related Parties					1.8		4.1					$ 1.8
Due to Related Parties					53.8		$ 148.7					$ 53.8
Contingent Commercialized Rights, Number Of Products \| product				2
Sangamo Therapeutics, Inc. Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Term of collaboration agreement												5 years
Other research and discovery
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and Development Expense (Excluding Acquired in Process Cost)					14.0			7.7				$ 51.5	84.9
InnoCare Pharma Limited (InnoCare) Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront and milestone payments made to collaborative partner		$ 125.0
Contingent additional milestone payment		$ 812.5
Research and development \| Eisai \| ADUHELM
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					34.6			43.7				116.0	132.8
Expense reflected within statements of income					19.0			24.0				63.8	73.0
Research and development \| Denali Therapeutics
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					19.9			8.5				58.0	27.2
Expense reflected within statements of income					11.4			5.1				33.5	16.3
Research and development \| Samsung Bioepis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					5.5			6.2			$ 16.4	16.4
Expense reflected within statements of income					3.1			1.9			$ 9.5	10.2
Research and development \| Sage Therapeutics Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					40.9			40.8				130.4	134.9
Expense reflected within statements of income					20.5			20.4				65.2	67.3
Research and development \| UCB Pharma S.A. [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					18.3			16.5				51.5	49.5
Expense reflected within statements of income					9.1			8.2				25.7	24.8
Selling, general and administrative \| Eisai \| BAN2401 and Elenbecestat
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					29.0			5.6				68.3	15.6
Expense reflected within statements of income					14.5			2.8				34.2	7.8
Selling, general and administrative \| Eisai \| ADUHELM
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					(8.0)			154.3				127.8	391.7
Expense reflected within statements of income					(3.9)			83.3				68.1	211.2
Selling, general and administrative \| Sage Therapeutics Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration					28.5			7.4				69.9	23.2
Expense reflected within statements of income					$ 14.2			$ 3.7				$ 34.9	$ 11.6

Collaborative and Other Relationships - Equity Method Investments (Details) ₩ in Millions, $ in Millions	1 Months Ended		3 Months Ended					9 Months Ended
	Apr. 30, 2022 USD ($)	Dec. 31, 2019	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 KRW (₩)	Jun. 30, 2022 KRW (₩)	Jan. 31, 2022 USD ($)	Dec. 31, 2021 KRW (₩)	Jan. 31, 2020 USD ($)	Nov. 07, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments								$ 2.6	$ 17.2
Collaboration profit (loss) sharing			$ 45.3			$ 21.2		(42.6)	74.5
ADUHELM
Schedule of Equity Method Investments [Line Items]
Research and development expense								$ 300.0
Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Percentage of stake in entity maximum			49.90%					49.90%		49.90%
Amortization of basis differences															$ 675.0
Loss recorded on Samsung Bioepis joint venture						1.1		$ 2.6	17.2
Income (loss) from equity method investments						8.9		17.0	39.5
Investment in Samsung Bioepis					$ 599.9					₩ 0.0			₩ 713,300.0
Collaboration profit (loss) sharing			$ 48.7			71.8		171.4	210.2
Eisai
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments			3.4			50.6		214.0	$ 90.7
Due to Related Parties			81.7		46.5			81.7
Eisai \| ADUHELM
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments				$ 59.0	45.0	$ 45.0		$ 177.0
Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Proceeds from divestiture of interest in joint venture	$ 1,000.0
Investment in Samsung Bioepis \| ₩											₩ 581.6
Payables to divestiture of interest in joint venture												$ 1,300.0
Equity Method Investments, Expected Profit Share		45.00%						50.00%
Upfront and milestone payments made to collaborative partner							$ 100.0
Research and development expense							$ 63.0
Prepaid research and development expenses														$ 37.0
Accrued milestone payments			15.0
Estimated additional payments upon achievement of development and commercial milestones								$ 180.0
Contract Option Exercise Fee								60.0
Due to Related Parties			$ 53.8		$ 148.7			$ 53.8
Samsung Bioepis \| Payment Due At First Anniversary
Schedule of Equity Method Investments [Line Items]
Payables to divestiture of interest in joint venture												812.5
Samsung Bioepis \| Payment Due At Second Anniversary
Schedule of Equity Method Investments [Line Items]
Payables to divestiture of interest in joint venture												$ 437.5
Inventory \| Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Equity method investment basis difference amortization period								1 year 6 months
Developed technology \| Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Equity method investment basis difference amortization period								15 years

Investments in Variable Interest Entities (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended				9 Months Ended
	Jun. 30, 2021	Sep. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Variable Interest Entity [Line Items]
(Gain) loss on equity method investments						$ 2.6	$ 17.2
Percentage of future development costs related to Eisai						45.00%
Deferred tax assets, net				$ 490.0
Deferred tax assets, unrecognized tax benefit		$ 85.0		390.0		$ 85.0
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities		25.3		24.6		$ 25.3
Neurimmune
Variable Interest Entity [Line Items]
Collaboration agreement term						12 years
Research and development costs, percentage						100.00%
Eisai
Variable Interest Entity [Line Items]
(Gain) loss on equity method investments		3.4			$ 50.6	$ 214.0	90.7
Percentage of future development costs related to Eisai					45.00%
Eisai \| ADUHELM
Variable Interest Entity [Line Items]
(Gain) loss on equity method investments			$ 59.0	45.0	$ 45.0	177.0
Additional milestone payment	$ 100.0	$ 0.0			$ 0.0	$ 0.0	$ 100.0
Eisai \| Regulatory Milestones \| Neurimmune \| ADUHELM
Variable Interest Entity [Line Items]
Potential future milestone payments commitment to third party				$ 100.0

Litigation (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
Litigation (Details) - USD ($) $ in Millions	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2020
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation agreement in principle	$ 0.0	$ 900.0	$ 0.0	$ 900.0	$ 0.0
Loss Contingency, Estimate of Possible Loss						$ 200.0

Dispositions (Details Textual) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
Dispositions (Details Textual) - USD ($) $ in Millions	Apr. 30, 2022	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Jan. 31, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of equity interest in Samsung Bioepis			$ (1,505.4)	$ 0.0
Samsung Bioepis
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity, ownership interest		49.90%	49.90%
Samsung Bioepis \| Fair Value, Recurring
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other current assets, receivable		$ 790.8	$ 790.8
Other assets, receivable		$ 402.8	$ 402.8
Samsung Bioepis \| Payment Due At First Anniversary \| Discount rate \| Fair Value, Recurring
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Risk-adjusted discount rates		0.049	0.049
Samsung Bioepis \| Payment Due At Second Anniversary \| Discount rate \| Fair Value, Recurring
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Risk-adjusted discount rates		0.053	0.053
Samsung Bioepis
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of interest in joint venture	$ 1,000.0
Payables to divestiture of interest in joint venture					$ 1,300.0
Gain on sale of equity interest in Samsung Bioepis			$ 1,500.0
Cumulative translation loss			58.9
Gain on derivative used in net investment hedge			57.0
Gain (loss) on sale		$ 2.7	(4.0)
Additional milestone payment	$ 50.0
Contingent discount on common shares	5.00%
Discrete income tax expense (benefit)		$ 258.3	$ 258.3
Samsung Bioepis \| Payment Due At First Anniversary
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payables to divestiture of interest in joint venture					812.5
Samsung Bioepis \| Payment Due At Second Anniversary
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payables to divestiture of interest in joint venture					$ 437.5