0000875045-20-000022 | 10-Q | XBRL Viewer

Earnings per Share (Tables)

6 Months Ended

Jun. 30, 2020

Basic and diluted earnings per share are calculated as follows:



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Numerator:
Net income attributable to Biogen Inc.	$	1,542.1	$	1,494.1	$	2,941.2	$	2,902.9
Denominator:
Weighted average number of common shares outstanding	160.6		190.3		166.7		193.4
Effect of dilutive securities:
Time-vested restricted stock units	0.1		0.1		0.1		0.2
Market stock units	0.1		—		0.1		0.1
Performance stock units settled in stock	0.1		—		0.1		—
Dilutive potential common shares	0.3		0.1		0.3		0.3
Shares used in calculating diluted earnings per share	160.9		190.4		167.0		193.7

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Total revenues	$ 3,681.6	$ 3,616.7	$ 7,215.9	$ 7,106.5
Cost and expenses:
Cost of sales, excluding amortization and impairment of acquired intangible assets	411.1	476.3	865.5	1,078.3
Research and development	647.6	484.8	1,123.9	1,048.5
Selling, general and administrative	555.1	587.6	1,125.2	1,155.3
Amortization and impairment of acquired intangible assets	61.5	70.1	133.0	138.3
Collaboration profit (loss) sharing	21.8	63.5	93.5	121.6
Loss on divestiture of Hillerød, Denmark manufacturing operations	0.0		0.0	113.2
(Gain) loss on fair value remeasurement of contingent consideration	10.0	(20.0)	5.5	(8.5)
Restructuring charges	0.0	0.8	0.0	1.2
Acquired in-process research and development	0.0	0.0	75.0	0.0
Total cost and expenses	1,707.1	1,660.8	3,421.6	3,647.9
Income from operations	1,974.5	1,955.9	3,794.3	3,458.6
Other income (expense), net	63.0	(197.4)	(57.5)	159.9
Income before income tax expense and equity in loss of investee, net of tax	2,037.5	1,758.5	3,736.8	3,618.5
Income tax expense	446.1	248.1	738.2	670.6
Equity in loss of investee, net of tax	(15.1)	16.3	(0.4)	45.0
Net income	1,606.5	1,494.1	2,999.0	2,902.9
Net income (loss) attributable to noncontrolling interests, net of tax	64.4	0.0	57.8	0.0
Net income attributable to Biogen Inc.	$ 1,542.1	$ 1,494.1	$ 2,941.2	$ 2,902.9
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 9.60	$ 7.85	$ 17.65	$ 15.01
Diluted earnings per share attributable to Biogen Inc.	$ 9.59	$ 7.85	$ 17.61	$ 14.99
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	160.6	190.3	166.7	193.4
Diluted earnings per share attributable to Biogen Inc.	160.9	190.4	167.0	193.7
Product, net
Total revenues	$ 2,795.7	$ 2,880.3	$ 5,700.3	$ 5,560.3
Revenues from anti-CD20 therapeutic programs
Total revenues	478.3	576.4	998.7	1,093.8
Other
Total revenues	$ 407.6	$ 160.0	$ 516.9	$ 452.4

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Common stock, par value	$ 0.0005	$ 0.0005

Intangible Assets and Goodwill (Details) - USD ($)	3 Months Ended		6 Months Ended
Intangible Assets and Goodwill (Details) - USD ($)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jun. 07, 2019
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets (Excluding Goodwill)	$ 0	$ 0	$ 0	$ 0
Intangible assets
Contingent consideration impairment	(10,000,000.0)	20,000,000.0	(5,500,000)	8,500,000
Total intangible assets, gross	8,398,200,000		8,398,200,000		$ 8,408,800,000
Accumulated Amortization	(5,014,400,000)		(5,014,400,000)		(4,881,400,000)
Intangible assets, net	3,383,800,000		3,383,800,000		3,527,400,000
Amortization and impairment of acquired intangible assets	61,500,000	$ 70,100,000	133,000,000.0	$ 138,300,000
Expected future amortization expense, 2019 (remaining three months)	126,000,000.0		126,000,000.0
Expected future amortization expense, 2020	220,000,000.0		220,000,000.0
Expected future amortization expense, 2021	220,000,000.0		220,000,000.0
Expected future amortization expense, 2022	230,000,000.0		230,000,000.0
Expected future amortization expense, 2023	230,000,000.0		230,000,000.0
Expected future amortization expense, 2024	220,000,000.0		220,000,000.0
Out-licensed patents
Intangible assets
Cost	7,379,300,000		7,379,300,000		7,379,300,000
Net	2,364,900,000		2,364,900,000		2,497,900,000
Accumulated Amortization	(5,014,400,000)		$ (5,014,400,000)		(4,881,400,000)
Out-licensed patents \| Minimum
Intangible assets
Estimated life, (in years)			13 years
Out-licensed patents \| Maximum
Intangible assets
Estimated life, (in years)			23 years
Developed technology \| Minimum
Intangible assets
Estimated life, (in years)			15 years
Developed technology \| Maximum
Intangible assets
Estimated life, (in years)			28 years
Acquired and in-licensed rights and patents \| Minimum
Intangible assets
Estimated life, (in years)			4 years
Acquired and in-licensed rights and patents \| Maximum
Intangible assets
Estimated life, (in years)			18 years
In Process Research and Development
Intangible assets
Indefinite lived intangible assets useful life			Indefinite until commercialization
Cost and Net	954,900,000		$ 954,900,000		965,500,000
Accumulated Amortization	0		$ 0		0
Trademarks and Trade Names
Intangible assets
Indefinite lived intangible assets useful life			Indefinite
Cost and Net	64,000,000.0		$ 64,000,000.0		64,000,000.0
Accumulated Amortization	0		0		$ 0
Nightstar
Intangible assets
In-process research and development						$ 700,000,000.0
TGN [Member] \| In Process Research and Development
Intangible assets
Cost and Net	$ 160,200,000		$ 160,200,000

Share-Based Payments (Details 1) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Share-Based Payments (Details 1) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	$ (49.5)	$ (55.0)	$ (118.8)	$ (104.0)
Subtotal	45.5	82.9	121.9	132.4
Capitalized share-based compensation costs	(1.5)	(2.8)	(3.0)	(6.1)
Share-based compensation expense included in total costs and expenses	44.0	80.1	118.9	126.3
Market stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	7.4	7.8	26.5	15.5
Time-vested restricted stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	34.5	31.8	72.0	66.5
Cash settled performance shares
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	(0.1)	0.4	(1.7)	(0.6)
Performance units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	0.0	0.3	(0.1)	0.8
Performance stock units settled in stock
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	2.1	12.1	12.4	14.1
Performance stock units settled in cash
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	(4.0)	0.9	4.9	1.9
Employee stock purchase plan
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	5.6	3.4	7.9	8.0
Nightstar \| Options
Summary of share based compensation expense associated with different programs [Abstract]
NST stock options	$ 0.0	$ 26.2	$ 0.0	$ 26.2

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2020

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. Our core growth areas include multiple sclerosis (MS) and neuroimmunology; Alzheimer's disease (AD) and dementia; neuromuscular disorders, including spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS); movement disorders, including Parkinson's disease; and ophthalmology. We are also focused on discovering, developing and delivering worldwide innovative therapies in our emerging growth areas of immunology; neurocognitive disorders; acute neurology; and pain. In addition, we commercialize biosimilars of advanced biologics. 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; and FUMADERM for the treatment of severe plaque psoriasis. We also 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 and relapsing MS; and other potential anti-CD20 therapies 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 consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2019 (2019 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 Samsung Bioepis Co., Ltd. (Samsung Bioepis), our joint venture with Samsung BioLogics Co., Ltd. (Samsung BioLogics), 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 and have exclusive rights to commercialize these products in China. Additionally, we have exclusive rights to commercialize two potential ophthalmology biosimilar products, SB11 referencing LUCENTIS and SB15 referencing EYLEA, in major markets worldwide, including the United States (U.S.), Canada, Europe, Japan and Australia. For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 17, 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 2019 Form 10-K. Our accounting policies are described in the Notes to Consolidated Financial Statements in our 2019 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 six months ended June 30, 2020, 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% of the economics, we record net income (loss) attributable to noncontrolling interests 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. These considerations impact the way we account for our existing collaborative relationships and other arrangements. 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, revenues and expenses and related disclosure of contingent assets and liabilities. On an ongoing basis we evaluate our estimates, judgments and methodologies. 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 revenues and expenses. Actual results may differ from these estimates.

The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including sales, expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, 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. We have made estimates of the impact of COVID-19 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 or may have a material impact on our condensed consolidated financial statements or disclosures.

Credit Losses

In June 2016 the FASB issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The FASB subsequently issued amendments to ASU 2016-13, which have the same effective date and transition date of January 1, 2020. This standard requires entities to estimate an expected lifetime credit loss on financial assets ranging from short-term trade accounts receivable to long-term financings and report credit losses using an expected losses model rather than the incurred losses model that was previously used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and requires the reversal of previously recognized credit losses if fair value increases.

This standard became effective for us on January 1, 2020, and based on the composition of our trade receivables, investment portfolio and other financial assets, current economic conditions and historical credit loss activity, the adoption of this standard did not have a material impact on our condensed consolidated financial statements and related disclosures. During the three and six months ended June 30, 2020, we recorded an immaterial amount associated with expected credit losses related to outstanding trade receivables in certain foreign countries that have been disproportionately impacted by the COVID-19 pandemic.

Fair Value Measurements

In August 2018 the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This standard modifies certain disclosure requirements on fair value measurements. This standard became effective for us on January 1, 2020, and did not have a material impact on our disclosures. For the new disclosures regarding our Level 3 instruments, please read Note 7, Fair Value Measurements, to these condensed consolidated financial statements.

Internal Use Software

In August 2018 the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This standard clarifies the accounting for implementation costs in cloud computing arrangements. This standard became effective for us on January 1, 2020, and was adopted on a prospective basis, resulting in an immaterial amount of additional assets being recorded on our condensed consolidated balance sheets.

Collaborative Arrangements

In November 2018 the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606. This standard makes targeted improvements for collaborative arrangements as follows:

•

Clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers, when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in ASC 606 should be applied, including recognition, measurement, presentation and disclosure requirements;


•	Adds unit-of-account guidance to ASC 808, Collaborative Arrangements, to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606; and


•	Precludes a company from presenting transactions with collaborative arrangement participants that are not directly related to sales to third parties with revenue recognized under ASC 606 if the collaborative arrangement participant is not a customer.

This standard became effective for us on January 1, 2020, and did not have a material impact on our condensed consolidated financial statements and related disclosures.

Indebtedness (Details) - USD ($)	6 Months Ended
Indebtedness (Details) - USD ($)	Jun. 30, 2020	Jun. 30, 2019	Apr. 30, 2020	Sep. 15, 2015
Debt Instrument [Line Items]
Payments of financing costs	$ 24,400,000
Derivative, gain on derivative	$ 3,300,000	$ 0
2.250% Senior Notes due May 1, 2030
Debt Instrument [Line Items]
Senior notes interest rate	2.25%
3.150% Senior Notes due May 1, 2050
Debt Instrument [Line Items]
Senior notes interest rate	3.15%
Senior Notes
Debt Instrument [Line Items]
Face amount			$ 3,000,000,000.0
Debt instrument, redemption price, percentage	100.00%
Debt instrument, make whole provision redemption price, percentage	101.00%
Senior Notes \| 2.250% Senior Notes due May 1, 2030
Debt Instrument [Line Items]
Face amount			$ 1,500,000,000
Senior notes interest rate			2.25%
Percentage par value of senior notes			99.973%
Senior Notes \| 3.150% Senior Notes due May 1, 2050
Debt Instrument [Line Items]
Face amount			$ 1,500,000,000
Senior notes interest rate			3.15%
Percentage par value of senior notes			99.174%
Senior Notes \| 2.90% Senior Notes Due Sept 15, 2020
Debt Instrument [Line Items]
Face amount				$ 1,500,000,000
Senior notes interest rate				2.90%
Percentage par value of senior notes				99.792%
Payment of early call premium and write off of remaining unamortized debt issuance costs	$ 12,700,000
Interest Expense \| Senior Notes \| 2.90% Senior Notes Due Sept 15, 2020
Debt Instrument [Line Items]
Pre-tax charge, payment of early call premium and write off of remaining unamortized debt issuance costs, net of derivative gain	9,400,000
Interest Expense \| Interest rate swap
Debt Instrument [Line Items]
Derivative, gain on derivative	$ 3,300,000

Collaborative and Other Relationships - Collaborations (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		3 Months Ended			6 Months Ended
	Feb. 29, 2020	Oct. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income			$ 15.1	$ (16.3)		$ 0.4	$ (45.0)
Eisai
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense Incurred By Collaboration			33.9	68.6		77.5	136.6
Expense reflected within statements of income			17.0	34.3		$ 38.7	68.3
Percentage of future development costs related to Eisai						45.00%
Loss on research and development contracts terminated with Eisai					$ 45.0
Additional Milestone Payment			75.0			$ 75.0
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income			33.8			33.8
Sangamo Therapeutics, Inc. Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Global Licensing Collaboration Agreement, Amount, Shares Purchased	$ 225.0
Global Licensing Collaboration Agreement, Shares, Purchased	24
Global Licensing Collaboration Agreement, Shares Purchased Per Share	$ 9.21
Upfront and milestone payments made to collaborative partner	$ 125.0
Global Licensing Collaboration Agreement, Research, Development, Regulatory and Commercial Milestone Payments	2,400.0
Global Licensing Collaboration Agreement, Payment, Selection of Targets	80.0
Global Licensing Collaboration Agreement, Payment, Achievement of First Commercial Sale Milestones	1,900.0
Global Licensing Collaboration Agreement, Payment, Achievement of Specific Sales Based Milestones	380.0
Research and development expense	$ 83.0
Skyhawk Therapeutics
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional Milestone Payment			2,400.0			2,400.0
Upfront and milestone payments made to collaborative partner		$ 15.0		74.0
Research and development expense				38.5
Prepaid research and development expenses				35.5			35.5
Research and development \| Eisai \| Aducanumab
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration			35.9	3.2		55.0	165.8
Expense reflected within statements of income			19.7	1.7		30.3	91.2
Research and development \| UCB Pharma S.A. [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration			6.5			25.5
Expense reflected within statements of income			3.2			12.7
Selling, general and administrative \| Eisai \| BAN2401 and Elenbecestat
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration			1.4			6.3
Expense reflected within statements of income			0.7			3.2
Selling, general and administrative \| Eisai \| Aducanumab
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expense incurred by the collaboration			45.2	0.2		67.9	21.2
Expense reflected within statements of income			$ 25.2	$ 0.1		$ 37.5	$ 11.7

Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Other Revenues (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 3,681.6	$ 3,616.7	$ 7,215.9	$ 7,106.5
Royalty
Disaggregation of Revenue [Line Items]
Total revenues	7.1	2.7	18.5	6.6
Other corporate revenues
Disaggregation of Revenue [Line Items]
Total revenues	395.5	105.2	489.5	369.3
Revenues related to amendment of contract manufacturing agreement	170.6		170.6		$ 500.0
Other
Disaggregation of Revenue [Line Items]
Total revenues	407.6	160.0	516.9	452.4
Collaborative arrangement \| Samsung Bioepis
Disaggregation of Revenue [Line Items]
Total revenues	0.5	(0.1)	0.7	(0.5)
Collaborative arrangement \| ZINBRYTA
Disaggregation of Revenue [Line Items]
Total revenues	$ 4.5	$ 52.2	$ 8.2	$ 77.0

Financial Instruments

6 Months Ended

Jun. 30, 2020

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 June 30, 2020		As of December 31, 2019
Commercial paper	$	139.9	$	384.4
Overnight reverse repurchase agreements	247.7		368.8
Money market funds	1,363.7		1,628.5
Short-term debt securities	118.3		159.4
Total	$	1,869.6	$	2,541.1

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:



As of June 30, 2020 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,282.5	$	1.5	$	(0.1	)	$	1,283.9
Non-current	502.8		3.8		(0.3		)	506.3
Government securities:
Current	657.7		0.5		—			658.2
Non-current	307.9		0.8		(0.1		)	308.6
Mortgage and other asset backed securities:
Current	0.6		—		—			0.6
Non-current	107.6		0.7		(0.4		)	107.9
Total marketable debt securities	$	2,859.1	$	7.3	$	(0.9	)	$	2,865.5
Marketable equity securities, non-current	$	428.0	$	114.6	$	(15.6	)	$	527.0



As of December 31, 2019 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,057.2	$	1.0	$	—		$	1,058.2
Non-current	633.9		3.0		—			636.9
Government securities:
Current	502.9		0.4		—			503.3
Non-current	510.1		0.8		(0.3		)	510.6
Mortgage and other asset backed securities:
Current	0.7		—		—			0.7
Non-current	260.2		0.8		(0.4		)	260.6
Total marketable debt securities	$	2,965.0	$	6.0	$	(0.7	)	$	2,970.3
Marketable equity securities, non-current	$	218.4	$	132.1	$	(13.0	)	$	337.5

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

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



	As of June 30, 2020				As of December 31, 2019
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,942.7	$	1,940.8	$	1,562.2	$	1,560.8
Due after one year through five years	862.6		858.5		1,234.5		1,230.4
Due after five years	60.2		59.8		173.6		173.8
Total marketable debt securities	$	2,865.5	$	2,859.1	$	2,970.3	$	2,965.0

The average maturity of our marketable debt securities available-for-sale as of June 30, 2020 and December 31, 2019, was approximately 14 months.

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Proceeds from maturities and sales	$	1,490.6		$	1,766.6		$	3,879.9		$	3,255.8
Realized gains	6.1			1.0			11.8			1.6
Realized losses	(5.2		)	(0.3		)	(24.3		)	(0.6		)

Strategic Investments

As of June 30, 2020 and December 31, 2019, our strategic investment portfolio was comprised of investments totaling $583.2 million and $393.9 million, respectively, which are included in 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 increase in our strategic investment portfolio for the three and six months ended June 30, 2020, was primarily due to our purchase of Sangamo common stock, as discussed below, and an increase in the fair value of our remaining investment in Ionis common stock.

For additional information on our June 2018 investment in Ionis common stock, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2019 Form 10-K.

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 AD; 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 will leverage Sangamo’s proprietary zinc finger protein technology delivered via AAV to modulate the expression of key genes involved in neurological diseases.

In connection with the closing of this transaction in April 2020 we purchased approximately 24 million shares of Sangamo common stock. This equity method investment will be remeasured each reporting period and carried at fair value due to our election of the fair value option. The effects of certain holding period restrictions on the investment are estimated using an option pricing valuation model. The most significant assumptions within the model are the term of the restrictions and the stock price volatility, which is based upon historical volatility of similar companies. We also use a constant maturity risk free-interest rate to match the remaining term of the restrictions on our investment in Sangamo’s common stock and a dividend yield of zero based upon the fact that Sangamo and similar companies generally have not historically granted cash dividends.

For additional information on our collaboration agreement with Sangamo, please read Note 17, Collaborative and Other Relationships, to these condensed consolidated financial statements.

Derivative Instruments (Details) $ in Millions, ₩ in Billions	1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
	Nov. 30, 2018 USD ($)	Nov. 30, 2018 KRW (₩)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Derivatives [Line Items]
Gain/Loss on fair value of foreign currency forward contracts			$ 16.8			$ 16.8		$ (0.5)
Gain on interest rate swap						3.3	$ 0.0
Gains (losses) on net investment hedges			(6.2)	$ 11.7		16.8	25.7
Net gains (losses) of other income (expense) related to foreign currency forward contracts			(8.3)	(0.9)		$ (5.9)	3.9
Minimum
Derivatives [Line Items]
Range of durations of foreign currency forward contracts						1 month		1 month
Maximum
Derivatives [Line Items]
Range of durations of foreign currency forward contracts						18 months		15 months
Not designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			999.3			$ 999.3		$ 793.8
Other current assets \| Designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			32.2			32.2		33.8
Other current assets \| Not designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			6.4			6.4		8.0
Other noncurrent assets \| Designated as hedging instrument
Derivatives [Line Items]
Derivative asset, fair value			0.7			0.7		0.0
Accrued expenses and other \| Designated as hedging instrument
Derivatives [Line Items]
Derivative liability, fair value			4.4			4.4		2.0
Accrued expenses and other \| Not designated as hedging instrument
Derivatives [Line Items]
Derivative liability, fair value			0.8			0.8		2.4
Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			2,773.4			2,773.4		1,892.4
Interest rate swap \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			675.0			675.0
Cash Flow Hedging [Member] \| Foreign exchange contract \| Other long-term liabilities
Derivatives [Line Items]
Derivative liability, fair value			9.0			9.0		1.7
Fair Value Hedging [Member] \| Interest rate swap \| Accrued expenses and other
Derivatives [Line Items]
Derivative liability, fair value			0.0			$ 0.0		2.3
Net Investment Hedging
Derivatives [Line Items]
Remaining duration of Net Investment Hedges						7 months
Unrealized gain (loss) on net investment hedges in AOCI						$ 13.9		1.5
Derivative qualifying as net investment hedge, excluded component			1.1			1.1		2.9
Gains (losses) on net investment hedges			(8.8)	11.6		15.4	23.4
Gains (losses) on net investment hedge, excluded component			3.5	2.3		3.2	6.7
Net Investment Hedging \| Foreign exchange contract \| Other current assets
Derivatives [Line Items]
Derivative asset, fair value			20.7			20.7		2.0
Interest Expense \| Interest rate swap
Derivatives [Line Items]
Gain on interest rate swap						3.3
Revenue \| Cash flows, revenue \| Foreign exchange contract
Derivatives [Line Items]
Gain (loss) on reclassification of cash flow hedges, effective portion			23.7	29.8		50.7	44.6
Gain (loss) recognized in net income, excluded component			(1.6)	3.7		7.7	7.4
Operating expense \| Cash flows, operating expenses \| Foreign exchange contract
Derivatives [Line Items]
Gain (loss) on reclassification of cash flow hedges, effective portion			0.0	(0.7)		(0.1)	(1.2)
Gain (loss) recognized in net income, excluded component			(0.2)	(0.3)		(1.1)	(1.2)
Other income (expense) \| Net Investment Hedging
Derivatives [Line Items]
Gain (loss) recognized in net income, excluded component			0.8	$ 2.2		1.7	$ 4.4
Euro \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			2,477.3			2,477.3		1,892.4
British pound \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			125.1			125.1		0.0
Swiss franc \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			69.0			69.0		0.0
Japan, Yen \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			53.9			53.9		0.0
Canadian dollar \| Foreign exchange contract \| Designated as hedging instrument
Derivatives [Line Items]
Derivative, Notional Amount			$ 48.1			$ 48.1		$ 0.0
2.900% Senior Notes due 2020
Derivatives [Line Items]
Senior notes interest rate			2.90%			2.90%
Samsung Bioepis
Derivatives [Line Items]
Percentage of stake in entity				5.00%			5.00%
Equity Method Investment, Ownership Percentage			49.90%			49.90%
Payments to acquire additional investment in equity method investment	$ 676.6	₩ 759.5			$ 676.6
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			$ 7.9			$ 7.9

Litigation (Details) SFr in Millions, $ in Millions	6 Months Ended
Litigation (Details) SFr in Millions, $ in Millions	Jun. 30, 2020 USD ($)	Jun. 30, 2020 CHF (SFr)	Dec. 31, 2019 USD ($)
Income Tax Contingency [Line Items]
Loss Contingency, Estimate of Possible Loss			$ 200.0
Disputed claims relating to construction costs	$ 33.0	SFr 31
Brazil
Income Tax Contingency [Line Items]
Brazil tax assessment, including interest and penalties	$ 70.0

Intangible Assets and Goodwill (Details 1) $ in Millions	6 Months Ended
Intangible Assets and Goodwill (Details 1) $ in Millions	Jun. 30, 2020 USD ($)
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period	$ 5,757.8
Other	(6.8)
Goodwill, end of period	5,751.0
Accumulated impairment losses related to goodwill	$ 0.0

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			$ (135.2)	$ (240.4)
Balance, January 1, 2018	$ (181.0)	$ (252.9)	(135.2)	(252.9)
Other comprehensive income (loss), before reclassifications, net of tax			(3.3)	36.0
Amounts reclassified from accumulated other comprehensive income, net of tax			(42.5)	(48.5)
Other comprehensive income (loss), net of tax	(30.6)	(33.5)	(44.0)	(12.9)
Accumulated other comprehensive income (loss), net of tax ending balance	(181.0)	(252.9)	(181.0)	(252.9)
Other comprehensive income (loss), net of tax	(31.7)	(33.1)	(45.8)	(12.5)
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			4.2	(4.0)
Balance, January 1, 2018	5.1	6.2	5.1	6.2
Other comprehensive income (loss), before reclassifications, net of tax			(9.0)	11.0
Amounts reclassified from accumulated other comprehensive income, net of tax			9.9	(0.8)
Other comprehensive income (loss), net of tax			0.9	10.2
Accumulated other comprehensive income (loss), net of tax ending balance	5.1	6.2	5.1	6.2
Unrealized gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			7.8	34.7
Balance, January 1, 2018	(9.6)	13.7	(9.6)	13.7
Other comprehensive income (loss), before reclassifications, net of tax			33.2	22.3
Amounts reclassified from accumulated other comprehensive income, net of tax			(50.6)	(43.3)
Other comprehensive income (loss), net of tax			(17.4)	(21.0)
Accumulated other comprehensive income (loss), net of tax ending balance	(9.6)	13.7	(9.6)	13.7
Gains (losses) on net investment hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			25.1	3.5
Balance, January 1, 2018	41.9	29.2	41.9	29.2
Other comprehensive income (loss), before reclassifications, net of tax			18.6	30.1
Amounts reclassified from accumulated other comprehensive income, net of tax			(1.8)	(4.4)
Other comprehensive income (loss), net of tax			16.8	25.7
Accumulated other comprehensive income (loss), net of tax ending balance	41.9	29.2	41.9	29.2
Unfunded status of postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			(32.8)	(31.3)
Balance, January 1, 2018	(31.9)	(30.6)	(31.9)	(30.6)
Other comprehensive income (loss), before reclassifications, net of tax			0.9	0.7
Amounts reclassified from accumulated other comprehensive income, net of tax			0.0	0.0
Other comprehensive income (loss), net of tax			0.9	0.7
Accumulated other comprehensive income (loss), net of tax ending balance	(31.9)	(30.6)	(31.9)	(30.6)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance			(139.5)	(243.3)
Balance, January 1, 2018	(186.5)	(271.4)	(186.5)	(271.4)
Other comprehensive income (loss), before reclassifications, net of tax			(47.0)	(28.1)
Amounts reclassified from accumulated other comprehensive income, net of tax			0.0	0.0
Other comprehensive income (loss), net of tax			(47.0)	(28.1)
Accumulated other comprehensive income (loss), net of tax ending balance	$ (186.5)	$ (271.4)	$ (186.5)	$ (271.4)

Collaborative and Other Relationships

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaborative and Other Relationships

Eisai Co., Ltd.

BAN2401 and Elenbecestat Collaboration

We have a collaboration agreement with Eisai Co., Ltd. (Eisai) to jointly develop and commercialize BAN2401, a monoclonal antibody that targets amyloid beta aggregates, and elenbecestat, the oral BACE (base amyloid cleaving enzyme) inhibitor, two Eisai product candidates for the potential treatment of AD (the BAN2401 and Elenbecestat Collaboration). In September 2019 we and Eisai discontinued the global Phase 3 studies of elenbecestat in early AD.

Eisai serves as the global operational and regulatory lead for BAN2401 and all costs, including research, development, sales and marketing expenses, are shared equally between us and Eisai. If BAN2401 receives marketing approval, we and Eisai will co-promote BAN2401 and share profits equally. In addition, the BAN2401 and Elenbecestat Collaboration provides both parties with certain rights and obligations in the event of a change in control of either party.

The BAN2401 and Elenbecestat Collaboration also provided Eisai with an option to jointly develop and commercialize aducanumab, our anti-amyloid beta antibody candidate for AD (Aducanumab Option), and an option to jointly develop and commercialize one of our anti-tau monoclonal antibodies (Anti-Tau Option). In October 2017 Eisai exercised its Aducanumab Option and we entered into a new collaboration agreement for the joint development and commercialization of aducanumab (Aducanumab Collaboration Agreement). Eisai has not yet exercised its Anti-Tau Option.

Under the Aducanumab Collaboration Agreement, the two companies will continue to jointly develop BAN2401 in accordance with the BAN2401 and Elenbecestat Collaboration; however, we are no longer required to pay Eisai any milestone payments for products containing BAN2401 and we are no longer entitled to any potential development and commercial milestone payments from Eisai in relation to aducanumab. For additional information on our BAN2401 and Elenbecestat Collaboration, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2019 Form 10-K.

A summary of development and sales and marketing expense related to the BAN2401 and Elenbecestat Collaboration is as follows:



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Total development expense incurred by the collaboration related to the advancement of BAN2401 and elenbecestat	$	33.9	$	68.6	$	77.5	$	136.6
Biogen's share of BAN2401 and elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income	17.0		34.3		38.7		68.3
Total sales and marketing expense incurred by the collaboration	1.4		nm		6.3		nm
Biogen's share of BAN2401 sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	0.7		nm		3.2		nm

^nm - For the three and six months ended June 30, 2019, sales and marketing expenses related to the BAN2401 and Elenbecestat Collaboration were immaterial.

Aducanumab Collaboration Agreement

Under the Aducanumab Collaboration Agreement, we and Eisai will co-promote aducanumab with a region-based profit split and we lead the ongoing development of aducanumab. Beginning January 1, 2019, Eisai is reimbursing us for 45% of development costs incurred by the collaboration for the advancement of aducanumab (aducanumab development expense).

In March 2019, based on a pre-specified futility analysis, we discontinued the global Phase 3 trials, EMERGE and ENGAGE, designed to evaluate the efficacy and safety of aducanumab in patients with early AD. A new analysis of a larger dataset from these trials, conducted in consultation with the FDA, showed that the Phase 3 EMERGE study met its pre-specified primary and secondary endpoints. In the first quarter of 2019, as a result of the decision to discontinue the Phase 3 EMERGE and ENGAGE trials following the futility analysis, we accrued approximately $45.0 million related to the termination of various clinical trials and research and development contracts net of the 45% Eisai reimbursement of development costs incurred under the Aducanumab Collaboration Agreement.

In July 2020 we completed the submission of a Biologics License Application (BLA) to the FDA for the approval of aducanumab. For the three and six months ended June 30, 2020, we recognized net profit-sharing income of $33.8 million to reflect Eisai's 45% share of the $75.0 million milestone expense related to the submission of the BLA to the FDA for approval of aducanumab.

Sales and marketing expense are shared in proportion to the same region-based profit split that will be utilized to co-promote aducanumab. For additional information on the Aducanumab Collaboration Agreement, please read Note 18, Collaborative and Other Relationships, to our consolidated financial statements included in our 2019 Form 10-K.

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



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Total aducanumab development expense	$	35.9	$	3.2	$	55.0	$	165.8
Biogen's share of aducanumab development expense reflected in research and development expense in our condensed consolidated statements of income	19.7		1.7		30.3		91.2
Total aducanumab sales and marketing expense	45.2		0.2		67.9		21.2
Biogen's share of aducanumab sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	25.2		0.1		37.5		11.7
Total aducanumab collaboration third party milestone expense	75.0		—		75.0		—
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income	33.8		—		33.8		—

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.

UCB Pharma S.A.

We have a collaboration agreement with UCB Pharma S.A. (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 expenses, are shared equally between us and UCB. Upon marketing approval, 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 June 30,			For the Six Months Ended June 30,
(In millions)	2020		2019	2020		2019
Total UCB development expense	$	6.5	nm	$	25.5	nm
Biogen's share of UCB development expense reflected in research and development expense in our condensed consolidated statements of income	3.2		nm	12.7		nm

^nm - For the three and six months ended June 30, 2019, development expenses related to the UCB collaboration agreement were immaterial.

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.

Sangamo Therapeutics, Inc.

In connection with the closing of this transaction in April 2020 we purchased $225.0 million of Sangamo common stock, or approximately 24 million shares at $9.21 per share, which are subject to transfer restrictions. We recorded an asset in investments and other assets in our condensed consolidated balance sheets to reflect the initial fair value of the Sangamo common stock acquired and a charge of approximately $83.0 million to research and development expense in our condensed consolidated statements of income to reflect the premium paid for the Sangamo common stock. We also made an upfront payment of $125.0 million that was recorded as research and development expense.

We may also pay research, development, regulatory and commercial milestone payments that could total up to approximately $2.4 billion if we select all of the targets allowed under this agreement and all the specified milestones set forth in this agreement are achieved. Of this amount, up to $80.0 million relates to the selection of targets, $1.9 billion relates to the achievement of specified research, clinical development, regulatory and first commercial sale milestones and $380.0 million relates to the achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels. In addition, we may pay tiered royalties on potential net commercial sales of any products developed under this collaboration in the high single digit to double digit sub-teen percentages.

Skyhawk Therapeutics, Inc.

In January 2019 we entered into a collaboration and research and development services agreement with Skyhawk Therapeutics, Inc. (Skyhawk) pursuant to which the companies are leveraging Skyhawk's SkySTAR technology platform with the goal of discovering innovative small molecule treatments for patients with neurological diseases, including MS and SMA. We are responsible for the development and potential commercialization of any therapies resulting from this collaboration and we may also pay Skyhawk up to a total of approximately $2.4 billion in milestone payments as well as potential royalties on net commercial sales.

In connection with this agreement, we made an upfront payment of $74.0 million to Skyhawk, of which $38.5 million was recorded as research and development expense in our condensed consolidated statements of income and $35.5 million was recorded as prepaid research and development expenditures within investments and other assets in our condensed consolidated balance sheets. These prepaid research and development services are expensed as the services are provided. In October 2019 we amended this agreement to add an additional discovery program. In connection with this amendment, we made a payment to Skyhawk of $15.0 million.

Samsung Bioepis

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 June 2018 we exercised our option under our joint venture agreement to increase our ownership percentage in Samsung Bioepis from approximately 5% 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. As of June 30, 2020, our ownership percentage remained at approximately 49.9%.

We recognize 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 become available, which is reflected as equity in income (loss) of investee, net of tax in our condensed consolidated statements of income. During 2015, as our share of losses exceeded the carrying value of our initial investment, we suspended recognizing additional losses. In the first quarter of 2019 we restarted recognizing our share of Samsung Bioepis' (income) losses, and we began recognizing amortization on certain basis differences resulting from our November 2018 investment.

Upon investment, the equity method of accounting requires 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 are amortized over their economic life. The total basis difference was approximately $675 million and relates to inventory, developed technology, IPR&D and deferred tax balances. The basis differences related to inventory and developed technology will be amortized, net of tax, over their estimated useful lives of 1.5 years and 15 years, respectively, one quarter in arrears.

Our joint venture partner, Samsung BioLogics, is currently subject to an ongoing criminal investigation that we continue to monitor. While this investigation could impact the operations of Samsung Bioepis and its business, we have assessed the value of our investment in Samsung Bioepis and continue to believe that the fair value of the investment is in excess of its net book value.

For the three and six months ended June 30, 2020, we recognized net income on our investment of $15.1 million and $0.4 million, respectively, reflecting our share of income and amortization of basis differences.

As of June 30, 2020 and December 31, 2019, the carrying value of our investment in Samsung Bioepis totaled 668.3 billion South Korean won ($557.5 million) and 670.8 billion South Korean won ($580.2 million), respectively, which is classified as a component of investments and other assets in our condensed consolidated balance sheets.

2019 Transaction

In December 2019 we completed a transaction with Samsung Bioepis and secured the exclusive rights to commercialize two potential ophthalmology biosimilar products, SB11 referencing LUCENTIS and SB15 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.

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 2019 and $37.0 million was recorded as an intangible asset in 2019. We may pay Samsung Bioepis up to $210.0 million in additional development, regulatory and sales-based milestones, including a $15.0 million development milestone which is expected to be paid during the third quarter of 2020.

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 exclusive rights to commercialize these products in China.

2013 Commercial Agreement

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

We share 50% 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 six months ended June 30, 2020, we recognized net profit-sharing expense of $55.4 million and $127.2 million, respectively, to reflect Samsung Bioepis' 50% sharing of the net collaboration profits, compared to $63.4 million and $121.5 million, respectively, in the prior year comparative periods. As discussed above, we have an option to extend this agreement by an additional five years, subject to the payment of an option exercise fee of $60.0 million.

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. For the three and six months ended June 30, 2020, we recognized $4.5 million and $8.2 million, respectively, in revenues related to these services, which is reflected in collaborative and other relationships revenues as a component of other revenues in our condensed consolidated statements of income, compared to $52.2 million and $77.0 million, respectively, in the prior year comparative periods.

Following the divestiture of our Hillerød, Denmark manufacturing operations in August 2019, FUJIFILM assumed responsibility for the manufacture of clinical and commercial quantities of bulk drug substance of biosimilar products for Samsung Bioepis. We no longer recognize revenues for the manufacturing completed after the Hillerød, Denmark manufacturing facility divestiture date under our technical development services and manufacturing agreements with Samsung Bioepis. For additional information on the divestiture of our Hillerød, Denmark manufacturing operations, please read Note 3, Divestitures, to these condensed consolidated financial statements.

Amounts receivable from Samsung Bioepis related to the agreements discussed above were $13.3 million and $85.0 million as of June 30, 2020 and December 31, 2019, respectively. There were no amounts payable to Samsung Bioepis as of June 30, 2020. Amounts payable to Samsung Bioepis as of December 31, 2019, consisted of the $100.0 million upfront payment related to the 2019 transaction, as discussed above.

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 2019 Form 10-K.

Revenues by Product (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Revenues by Product (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Product revenues	$ 3,681.6	$ 3,616.7	$ 7,215.9	$ 7,106.5
Fumarate
Disaggregation of Revenue [Line Items]
Product revenues	1,190.3	1,150.2	2,291.1	2,149.0
Fumarate \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	921.7	869.8	1,699.2	1,587.5
Fumarate \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	268.6	280.4	591.9	561.5
Interferon
Disaggregation of Revenue [Line Items]
Product revenues	481.4	554.4	947.4	1,055.3
Interferon \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	345.6	379.7	638.2	707.0
Interferon \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	135.8	174.7	309.2	348.3
TYSABRI
Disaggregation of Revenue [Line Items]
Product revenues	432.0	475.3	954.4	935.7
TYSABRI \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	244.1	264.3	521.8	509.3
TYSABRI \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	187.9	211.0	432.6	426.4
FAMPYRA
Disaggregation of Revenue [Line Items]
Product revenues	23.0	24.1	51.3	47.0
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	23.0	24.1	51.3	47.0
MS Product Revenues
Disaggregation of Revenue [Line Items]
Product revenues	2,126.7	2,204.0	4,244.2	4,187.0
MS Product Revenues \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	1,511.4	1,513.8	2,859.2	2,803.8
MS Product Revenues \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	615.3	690.2	1,385.0	1,383.2
SPINRAZA
Disaggregation of Revenue [Line Items]
Product revenues	494.6	488.2	1,059.6	1,006.7
SPINRAZA \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	210.3	230.6	445.7	453.9
SPINRAZA \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	284.3	257.6	613.9	552.8
BENEPALI
Disaggregation of Revenue [Line Items]
Product revenues	106.2	120.3	239.7	244.3
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	106.2	120.3	239.7	244.3
IMRALDI
Disaggregation of Revenue [Line Items]
Product revenues	44.8	47.3	106.4	83.0
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	44.8	47.3	106.4	83.0
FLIXABI
Disaggregation of Revenue [Line Items]
Product revenues	20.6	16.8	44.3	31.5
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	20.6	16.8	44.3	31.5
Biosimilars
Disaggregation of Revenue [Line Items]
Product revenues	171.6	184.4	390.4	358.8
Biosimilars \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	0.0	0.0	0.0	0.0
Biosimilars \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	171.6	184.4	390.4	358.8
FUMADERM
Disaggregation of Revenue [Line Items]
Product revenues	2.8	3.7	6.1	7.8
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	2.8	3.7	6.1	7.8
Product, net
Disaggregation of Revenue [Line Items]
Product revenues	2,795.7	2,880.3	5,700.3	5,560.3
Product, net \| U.S.
Disaggregation of Revenue [Line Items]
Product revenues	1,721.7	1,744.4	3,304.9	3,257.7
Product, net \| Rest of World
Disaggregation of Revenue [Line Items]
Product revenues	$ 1,074.0	$ 1,135.9	$ 2,395.4	$ 2,302.6

Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 1,687.0		$ 1,687.0		$ 1,590.9
Depreciation	51.3	$ 47.0	99.7	$ 99.9
Solothurn, Switzerland
Property, Plant and Equipment [Line Items]
Construction in progress	1,700.0		1,700.0		$ 1,900.0
Fixed assets placed into service	256.8		256.8
Contractual commitments for the construction of the facility	$ 16.2		$ 16.2

Other Consolidated Financial Statement Detail

6 Months Ended

Jun. 30, 2020

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Interest income	$	7.6		$	29.1		$	32.0		$	60.3
Interest expense	(66.0		)	(47.7		)	(110.3		)	(95.6		)
Gain (loss) on investments, net	106.8			(173.4		)	29.5			203.0
Foreign exchange gains (losses), net	10.4			1.7			(8.5		)	(0.5		)
Other, net	4.2			(7.1		)	(0.2		)	(7.3		)
Total other income (expense), net	$	63.0		$	(197.4	)	$	(57.5	)	$	159.9

Gain (loss) 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.

For the three months ended June 30, 2020, compared to the same period in 2019, the change in other income (expense), net primarily reflects net gains of approximately $106.8 million recognized on our investments related to our holdings in equity and debt securities, compared to net losses totaling $173.4 million in the prior year comparative period. The net gains recognized during the three months ended June 30, 2020, primarily reflect an increase in the fair value of Ionis common stock of approximately $67.2 million and an increase in the fair value of Sangamo common stock of approximately $40.9 million.

For the six months ended June 30, 2020, compared to the same period in 2019, the change in other income (expense), net was primarily due to approximately $203.0 million of net gains recognized on our investments related to our holdings in equity and debt securities during the six months ended June 30, 2019.

The following table summarizes our gain (loss) on investments, net that relates to our equity securities held as of June 30, 2020 and 2019:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Net gains (losses) recognized during the period on equity securities	$	102.9	$	(174.2	)	$	42.0	$	201.9
Less: Net gains (losses) recognized during the period on equity securities sold during the period	—		(42.9		)	—		42.4
Unrealized gains (losses) recognized during the period on equity securities	$	102.9	$	(131.3	)	$	42.0	$	159.5

Accrued Expenses and Other

Accrued expenses and other consists of the following:



(In millions)	As of June 30, 2020		As of December 31, 2019
Revenue-related reserves for discounts and allowances	$	951.3	$	1,001.1
Employee compensation and benefits	212.0		309.1
Royalties and licensing fees	203.0		220.9
Collaboration expenses	172.9		281.6
Current portion of contingent consideration obligations	149.1		148.4
Construction in progress	24.1		78.0
Other	774.1		726.7
Total accrued expenses and other	$	2,486.5	$	2,765.8

Other Long-term Liabilities

Other long-term liabilities were $1,475.4 million and $1,348.9 million as of June 30, 2020 and December 31, 2019, respectively, and included accrued income taxes totaling $743.2 million and $803.3 million, respectively. Included within accrued taxes as of June 30, 2020 and December 31, 2019, is an accrual for a one-time mandatory deemed repatriation tax on accumulated foreign subsidiaries' previously untaxed foreign earnings (the Transition Toll Tax) of approximately $635.0 million and approximately $697.0 million, respectively.

Revenues (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Revenues (Details Textual) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Other Revenues	$ 3,681.6	$ 3,616.7	$ 7,215.9	$ 7,106.5
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	31.70%	30.50%	30.80%	30.90%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	17.90%	18.20%	16.20%	16.30%
Other corporate revenues
Disaggregation of Revenue [Line Items]
Revenues related to amendment of contract manufacturing agreement	$ 170.6		$ 170.6		$ 500.0
Other Revenues	395.5	$ 105.2	489.5	$ 369.3
Other corporate revenues \| Contract Manufacturing Customer
Disaggregation of Revenue [Line Items]
Other Revenues	329.4		329.4
Other
Disaggregation of Revenue [Line Items]
Other Revenues	$ 407.6	$ 160.0	$ 516.9	$ 452.4

Fair Value Measurements (Details 1) - USD ($)	Jun. 30, 2020	Apr. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Notes payable, carrying value	$ 7,423,800,000		$ 5,954,800,000
Debt instruments, fair value	8,257,600,000		6,553,600,000
2.900% Senior Notes due 2020
Debt Instrument [Line Items]
Notes payable, fair value	0		1,509,600,000
Notes payable, carrying value	$ 0		1,495,800,000
Senior notes interest rate	2.90%
3.625% Senior Notes due 2022
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,061,000,000.0		1,038,900,000
Notes payable, carrying value	$ 997,300,000		996,600,000
Senior notes interest rate	3.625%
4.050% Senior Notes due 2025
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,994,100,000		1,897,200,000
Notes payable, carrying value	$ 1,740,300,000		1,739,500,000
Senior notes interest rate	4.05%
2.250% Senior Notes due May 1, 2030
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,514,100,000		0
Notes payable, carrying value	$ 1,490,700,000		0
Senior notes interest rate	2.25%
5.200% Senior Notes due 2045
Debt Instrument [Line Items]
Notes payable, fair value	$ 2,247,100,000		2,107,900,000
Notes payable, carrying value	$ 1,723,200,000		1,722,900,000
Senior notes interest rate	5.20%
3.150% Senior Notes due May 1, 2050
Debt Instrument [Line Items]
Notes payable, fair value	$ 1,441,300,000		0
Notes payable, carrying value	$ 1,472,300,000		$ 0
Senior notes interest rate	3.15%
Senior Notes
Debt Instrument [Line Items]
Face amount		$ 3,000,000,000.0
Senior Notes \| 2.250% Senior Notes due May 1, 2030
Debt Instrument [Line Items]
Senior notes interest rate		2.25%
Face amount		$ 1,500,000,000
Senior Notes \| 3.150% Senior Notes due May 1, 2050
Debt Instrument [Line Items]
Senior notes interest rate		3.15%
Face amount		$ 1,500,000,000

Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Fair Value Measurements (Details 2) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration impairment	$ (10.0)	$ 20.0	$ (5.5)	$ 8.5
Payments	0.0	0.0	0.0	0.0
Fair Value, Measurements, Recurring
Business Acquisition, Contingent Consideration [Line Items]
Fair value, beginning of period	341.6	421.3	346.1	409.8
Fair value, end of period	$ 351.6	$ 401.3	$ 351.6	$ 401.3

Reserves for Discounts and Allowances (Details 2) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Total Reserves	$ 1,174.7	$ 1,198.9
Reduction of accounts receivable
Total Reserves	223.4	197.8
Component of accrued expenses and other
Total Reserves	$ 951.3	$ 1,001.1

Financial Instruments (Details 3) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Financial Instruments (Details 3) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Proceeds from maturities and sales	$ 1,490.6	$ 1,766.6	$ 3,879.9	$ 3,255.8
Realized gains	6.1	1.0	11.8	1.6
Realized losses	$ (5.2)	$ (0.3)	$ (24.3)	$ (0.6)

Share-Based Payments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Share-Based Payments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	$ (49.5)	$ (55.0)	$ (118.8)	$ (104.0)
Subtotal	45.5	82.9	121.9	132.4
Capitalized share-based compensation costs	(1.5)	(2.8)	(3.0)	(6.1)
Share-based compensation expense included in total costs and expenses	44.0	80.1	118.9	126.3
Income tax effect	(7.0)	(13.6)	(20.3)	(21.0)
Research and development
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	15.2	28.1	48.5	49.8
Selling, general and administrative
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	30.3	54.8	73.4	82.6
Total share-based compensation expense, net of tax
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	$ 37.0	$ 66.5	$ 98.6	$ 105.3

Indebtedness (Notes)	6 Months Ended
Indebtedness (Notes)	Jun. 30, 2020
Debt Disclosure [Abstract]
Indebtedness	Indebtedness 2020 Senior Notes On April 30, 2020, we issued senior unsecured notes for an aggregate principal amount of $3.0 billion (2020 Senior Notes), consisting of the following: •$1.5 billion of 2.25% Senior Notes due May 1, 2030, valued at 99.973% of par; and •$1.5 billion of 3.15% Senior Notes due May 1, 2050, valued at 99.174% of par. Our 2020 Senior Notes are senior unsecured obligations and may be redeemed at our option at any time at 100% of the principal amount plus accrued interest and, until a specified period before maturity, a specified make-whole amount. Our 2020 Senior Notes contain a change-of-control provision that, under certain circumstances, may require us to purchase our 2020 Senior Notes at a price equal to 101% of the principal amount plus accrued and unpaid interest to the date of repurchase. We incurred approximately $24.4 million of costs associated with this offering which have been recorded as a reduction to the carrying amount of the debt on our condensed consolidated balance sheet. These costs will be amortized as additional interest expense using the effective interest rate method over the period from issuance through maturity. The discounts will be amortized as additional interest expense over the period from issuance through maturity using the effective interest rate method. Interest on our 2020 Senior Notes is payable May 1 and November 1 of each year, commencing November 1, 2020. 2.90% Senior Notes due September 15, 2020 On September 15, 2015, we issued $1.5 billion aggregate principal amount of 2.90% Senior Notes due September 15, 2020, at 99.792% of par. Our 2.90% Senior Notes were senior unsecured obligations. We also entered into interest rate swap contracts where we received a fixed rate and paid a variable rate. In May 2020 we used the net proceeds from the sale of our 2020 Senior Notes to redeem our 2.90% Senior Notes prior to their maturity and recognized a net pre-tax charge of $9.4 million upon the extinguishment of these notes. This charge, which was recognized in interest expense in other income (expense), net in our condensed consolidated statements of income for the three and six months ended June 30, 2020, reflects the payment of a $12.7 million early call premium and the write off of remaining unamortized original debt issuance costs and discount balances, partially offset by a $3.3 million gain related to the settlement of the associated interest rate swap contracts. For additional information on our interest rate swap contracts, please read Note 9, Derivative Instruments, to these condensed consolidated financial statements.

Revenues from Anti-CD20 Therapeutic Programs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues from anti-CD20 therapeutic programs	$ 3,681.6	$ 3,616.7	$ 7,215.9	$ 7,106.5
Genentech
Disaggregation of Revenue [Line Items]
Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	257.5	377.2	598.8	768.0
Other revenues from anti-CD20 therapeutic programs	220.8	199.2	399.9	325.8
Revenues from anti-CD20 therapeutic programs
Disaggregation of Revenue [Line Items]
Total revenues from anti-CD20 therapeutic programs	$ 478.3	$ 576.4	$ 998.7	$ 1,093.8

Intangible Assets and Goodwill

6 Months Ended

Jun. 30, 2020

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 June 30, 2020							As of December 31, 2019
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Completed technology	4-28 years	$	7,379.3	$	(5,014.4	)	$	2,364.9	$	7,379.3	$	(4,881.4	)	$	2,497.9
In-process research and development	Indefinite until commercialization	954.9		—			954.9		965.5		—			965.5
Trademarks and trade names	Indefinite	64.0		—			64.0		64.0		—			64.0
Total intangible assets		$	8,398.2	$	(5,014.4	)	$	3,383.8	$	8,408.8	$	(4,881.4	)	$	3,527.4

For the three and six months ended June 30, 2020, amortization and impairment of acquired intangible assets totaled $61.5 million and $133.0 million, respectively, compared to $70.1 million and $138.3 million, respectively, in the prior year comparative periods. We had no impairment charges for the three and six months ended June 30, 2020 and 2019.

Completed Technology

Completed technology primarily relates to our acquisition of all remaining rights to TYSABRI from Elan Pharma International Ltd., an affiliate of Elan Corporation plc, and milestone payments made to Alkermes Pharma Ireland Limited, a subsidiary of Alkermes plc, following the approval of VUMERITY in the U.S. in October 2019, net of accumulated amortization.

IPR&D Related to Business Combinations

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 June 30, 2020, relates to the various IPR&D programs we acquired in connection with our acquisitions of NST, Convergence Pharmaceuticals Holdings Ltd. (Convergence) and Biogen International Neuroscience GmbH (BIN). The majority of the balance relates to our acquisition of NST in June 2019 whereby we acquired IPR&D programs with an estimated fair value of approximately $700.0 million.

Vixotrigine

In the periods since we acquired vixotrigine (BIIB074), there have been numerous delays in the initiation of Phase 3 studies for the potential treatment of trigeminal neuralgia (TGN) as we engaged with the U.S. Food and Drug Administration (FDA) regarding the design of the Phase 3 studies and awaited data and insights from mid-stage clinical trials of vixotrigine in other indications that have since been completed. The fair value of the TGN asset is not significantly in excess of carrying value. As of June 30, 2020, the carrying value associated with our vixotrigine IPR&D assets was $160.2 million.

Estimated Future Amortization of Intangible Assets

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



(In millions)	As of June 30, 2020
2020 (remaining six months)	$	126.0
2021	220.0
2022	220.0
2023	230.0
2024	230.0
2025	220.0

Goodwill

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



(In millions)	As of June 30, 2020
Goodwill, beginning of period	$	5,757.8
Other	(6.8		)
Goodwill, end of period	$	5,751.0

As of June 30, 2020, we had no accumulated impairment losses related to goodwill. Other includes adjustments related to foreign currency exchange rate fluctuations.

Investments in Variable Interest Entities (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	May 31, 2018	Oct. 31, 2017	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Payments to Noncontrolling Interests					$ 0.0	$ (4.3)
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities			$ 22.4		22.4		$ 22.7
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income			15.1	$ (16.3)	0.4	$ (45.0)
Neurimmune
Variable Interest Entity [Line Items]
Payments to Noncontrolling Interests	$ 50.0	$ 150.0
Reduction in royalty rate payable on commercial sales		15.00%
Additional reduction in royalty rate payable on commercial sales	5.00%
Regulatory Milestones [Member] \| Neurimmune
Variable Interest Entity [Line Items]
Potential Future Milestone Payments Commitment To Third Party Approximately							75.0
Regulatory Approval Milestone [Member] \| Neurimmune
Variable Interest Entity [Line Items]
Potential Future Milestone Payments Commitment To Third Party Approximately							$ 100.0
Eisai
Variable Interest Entity [Line Items]
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income			$ 33.8		$ 33.8
Percentage of future development costs related to Eisai					45.00%

Share-based Payments

6 Months Ended

Jun. 30, 2020

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Research and development	$	15.2		$	28.1		$	48.5		$	49.8
Selling, general and administrative	30.3			54.8			73.4			82.6
Subtotal	45.5			82.9			121.9			132.4
Capitalized share-based compensation costs	(1.5		)	(2.8		)	(3.0		)	(6.1		)
Share-based compensation expense included in total cost and expenses	44.0			80.1			118.9			126.3
Income tax effect	(7.0		)	(13.6		)	(20.3		)	(21.0		)
Share-based compensation expense included in net income attributable to Biogen Inc.	$	37.0		$	66.5		$	98.6		$	105.3

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



	For the Three Months Ended June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Market stock units	$	7.4		$	7.8		$	26.5		$	15.5
Time-vested restricted stock units	34.5			31.8			72.0			66.5
Cash settled performance units	(0.1		)	0.4			(1.7		)	(0.6		)
Performance units	—			0.3			(0.1		)	0.8
Performance stock units settled in stock	2.1			12.1			12.4			14.1
Performance stock units settled in cash	(4.0		)	0.9			4.9			1.9
Employee stock purchase plan	5.6			3.4			7.9			8.0
NST stock options	—			26.2			—			26.2
Subtotal	45.5			82.9			121.9			132.4
Capitalized share-based compensation costs	(1.5		)	(2.8		)	(3.0		)	(6.1		)
Share-based compensation expense included in total cost and expenses	$	44.0		$	80.1		$	118.9		$	126.3

We estimate the fair value of our obligations associated with our performance units, cash settled performance units and 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.

Fair Value Measurements

6 Months Ended

Jun. 30, 2020

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:



As of June 30, 2020 (In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,869.6	$	—	$	1,869.6	$	—
Marketable debt securities:
Corporate debt securities	1,790.2		—		1,790.2		—
Government securities	966.8		—		966.8		—
Mortgage and other asset backed securities	108.5		—		108.5		—
Marketable equity securities	527.0		344.3		182.7		—
Derivative contracts	59.9		—		59.9		—
Plan assets for deferred compensation	27.7		—		27.7		—
Total	$	5,349.7	$	344.3	$	5,005.4	$	—
Liabilities:
Derivative contracts	$	14.3	$	—	$	14.3	$	—
Contingent consideration obligations	351.6		—		—		351.6
Total	$	365.9	$	—	$	14.3	$	351.6



As of December 31, 2019 (In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,541.1	$	—	$	2,541.1	$	—
Marketable debt securities:
Corporate debt securities	1,695.1		—		1,695.1		—
Government securities	1,013.9		—		1,013.9		—
Mortgage and other asset backed securities	261.3		—		261.3		—
Marketable equity securities	337.5		7.9		329.6		—
Derivative contracts	43.8		—		43.8		—
Plan assets for deferred compensation	27.7		—		27.7		—
Total	$	5,920.4	$	7.9	$	5,912.5	$	—
Liabilities:
Derivative contracts	$	8.3	$	—	$	8.3	$	—
Contingent consideration obligations	346.1		—		—		346.1
Total	$	354.4	$	—	$	8.3	$	346.1

There have been no material impairments of our assets measured and carried at fair value during the three and six months ended June 30, 2020. In addition, there were no changes in valuation techniques during the three and six months ended June 30, 2020. The fair value of Level 2 instruments classified as cash equivalents and marketable debt securities was determined through third-party pricing services. The fair value of Level 2 instruments classified as marketable equity securities represents our investment in Sangamo Therapeutics, Inc. (Sangamo) common stock and is valued using an option pricing valuation model as the investment is subject to certain holding period restrictions. For additional information on our investment in Sangamo common stock, please read Note 8, Financial Instruments, to these condensed consolidated financial statements

Our investments in marketable equity securities also include shares of Ionis Pharmaceuticals, Inc. (Ionis) common stock acquired in June 2018. Our shares in Ionis common stock were initially subject to certain holding period restrictions that expired during the first quarter of 2020. The fair value of this investment was a Level 1 measurement as of June 30, 2020.

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 2019 Form 10-K.

The following table summarizes the significant unobservable inputs in the fair value measurement of our contingent consideration obligations as of June 30, 2020:

As of June 30, 2020

(In millions)

Fair Value

Valuation Technique

Unobservable Input

Range

Weighted Average

Liabilities:

Contingent consideration obligation

351.6

Discounted cash flow

Discount rate

0.83% to 1.18%

0.92%

Timing of achievement of development milestones

2021 to 2027

—

The weighted average discount rate was calculated based on the relative fair value of our contingent consideration obligations. In addition, we apply various probabilities of technological and regulatory success, ranging from high single digits to certain probability, to the valuation models to estimate the fair values of our contingent consideration obligations.

Debt Instruments

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



	As of June 30, 2020				As of December 31, 2019
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
2.900% Senior Notes due September 15, 2020⁽¹⁾	$	—	$	—	$	1,509.6	$	1,495.8
3.625% Senior Notes due September 15, 2022	1,061.0		997.3		1,038.9		996.6
4.050% Senior Notes due September 15, 2025	1,994.1		1,740.3		1,897.2		1,739.5
2.250% Senior Notes due May 1, 2030	1,514.1		1,490.7		—		—
5.200% Senior Notes due September 15, 2045	2,247.1		1,723.2		2,107.9		1,722.9
3.150% Senior Notes due May 1, 2050	1,441.3		1,472.3		—		—
Total	$	8,257.6	$	7,423.8	$	6,553.6	$	5,954.8

⁽¹⁾As of June 30, 2020, our 2.900% Senior Notes due September 15, 2020, were redeemed in full using the net proceeds from the issuance on April 30, 2020, of our senior unsecured notes for an aggregate principal amount of $3.0 billion. For additional information, please read Note 11, 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. For additional information related to our Senior Notes issued on September 15, 2015, please read Note 12, Indebtedness, to our consolidated financial statements included in our 2019 Form 10-K. For additional information related to our Senior Notes issued on April 30, 2020, please read Note 11, Indebtedness, to these condensed consolidated financial statements.

Contingent Consideration Obligations

In connection with our acquisitions of Convergence and BIN, 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 includes Level 3 measurements:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Fair value, beginning of period	$	341.6	$	421.3		$	346.1	$	409.8
Changes in fair value	10.0		(20.0		)	5.5		(8.5		)
Payments	—		—			—		—
Fair value, end of period	$	351.6	$	401.3		$	351.6	$	401.3

As of June 30, 2020 and December 31, 2019, approximately $202.5 million and $197.7 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 the remaining balance reflected as a component of accrued expenses and other.

For the three and six months ended June 30, 2020, changes in the fair value of our contingent consideration obligations were primarily due to changes in the interest rates used to revalue our contingent consideration liabilities, changes in the probability and the expected timing of the achievement of certain remaining developmental milestones and the passage of time.

For the three and six months ended June 30, 2019, changes in the fair value of our contingent consideration obligations were primarily due to changes in the probability and the expected timing of the achievement of certain remaining development milestones, partially offset by a decrease in interest rates used to revalue our contingent consideration liabilities and the passage of time.

- 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

Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Other Income (Expense), Net
Interest income	$ 7.6	$ 29.1	$ 32.0	$ 60.3
Interest expense	(66.0)	(47.7)	(110.3)	(95.6)
Gain (loss) on investments, net	106.8	(173.4)	29.5	203.0
Foreign exchange gains (losses), net	10.4	1.7	(8.5)	(0.5)
Other, net	4.2	(7.1)	(0.2)	(7.3)
Total other income (expense), net	63.0	(197.4)	(57.5)	159.9
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net gains (losses) recognized during the period on equity securities	102.9	(174.2)	42.0	201.9
Less: Net gains (losses) recognized during the period on equity securities sold during the period	0.0	(42.9)	0.0	(42.4)
Unrealized gains (losses) recognized during the period on equity securities held as of March 31	102.9	$ (131.3)	42.0	$ 159.5
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	1,174.7		1,174.7		$ 1,198.9
Collaboration expenses	212.0		212.0		309.1
Royalties and licensing fees	203.0		203.0		220.9
Collaboration expenses	172.9		172.9		281.6
Current portion of contingent consideration obligations	149.1		149.1		148.4
Construction in progress	24.1		24.1		78.0
Other	774.1		774.1		726.7
Total accrued expenses and other	2,486.5		2,486.5		2,765.8
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 951.3		$ 951.3		$ 1,001.1

Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Assets:
Marketable debt securities	$ 2,865.5		$ 2,970.3
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	1,869.6		2,541.1
Marketable equity securities	527.0		337.5
Derivative contracts	59.9		43.8
Plan assets for deferred compensation	27.7		27.7
Total	5,349.7		5,920.4
Liabilities:
Derivative contracts	14.3		8.3
Contingent consideration obligations	351.6	$ 341.6	346.1	$ 401.3	$ 421.3	$ 409.8
Total	365.9		354.4
Fair Value, Measurements, Recurring \| Corporate debt securities
Assets:
Marketable debt securities	1,790.2		1,695.1
Fair Value, Measurements, Recurring \| Government securities
Assets:
Marketable debt securities	966.8		1,013.9
Fair Value, Measurements, Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	108.5		261.3
Quoted Prices in Active Markets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0		0.0
Marketable equity securities	344.3		7.9
Derivative contracts	0.0		0.0
Plan assets for deferred compensation	0.0		0.0
Total	344.3		7.9
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 \| 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	1,869.6		2,541.1
Marketable equity securities	182.7		329.6
Derivative contracts	59.9		43.8
Plan assets for deferred compensation	27.7		27.7
Total	5,005.4		5,912.5
Liabilities:
Derivative contracts	14.3		8.3
Contingent consideration obligations	0.0		0.0
Total	14.3		8.3
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring \| Corporate debt securities
Assets:
Marketable debt securities	1,790.2		1,695.1
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring \| Government securities
Assets:
Marketable debt securities	966.8		1,013.9
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring \| Mortgage and other asset backed securities
Assets:
Marketable debt securities	108.5		261.3
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	0.0		0.0
Liabilities:
Derivative contracts	0.0		0.0
Contingent consideration obligations	351.6		346.1
Total	351.6		346.1
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

Collaborative and Other Relationships (Tables)

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Activity Related to BAN2401 and Elenbecestat Collaboration



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Total development expense incurred by the collaboration related to the advancement of BAN2401 and elenbecestat	$	33.9	$	68.6	$	77.5	$	136.6
Biogen's share of BAN2401 and elenbecestat development expense reflected in research and development expense in our condensed consolidated statements of income	17.0		34.3		38.7		68.3
Total sales and marketing expense incurred by the collaboration	1.4		nm		6.3		nm
Biogen's share of BAN2401 sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	0.7		nm		3.2		nm

Summary of Activity Related to Aducanumab Collaboration

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



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Total aducanumab development expense	$	35.9	$	3.2	$	55.0	$	165.8
Biogen's share of aducanumab development expense reflected in research and development expense in our condensed consolidated statements of income	19.7		1.7		30.3		91.2
Total aducanumab sales and marketing expense	45.2		0.2		67.9		21.2
Biogen's share of aducanumab sales and marketing expense reflected in selling, general and administrative expense in our condensed consolidated statements of income	25.2		0.1		37.5		11.7
Total aducanumab collaboration third party milestone expense	75.0		—		75.0		—
Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our condensed consolidated statements of income	33.8		—		33.8		—

Accumulated Other Comprehensive Income (Loss) (Tables)

6 Months Ended

Jun. 30, 2020

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 Hedge			Unfunded Status of Postretirement Benefit Plans, Net of Tax			Currency Translation Adjustments			Total
Balance, December 31, 2019	$	4.2		$	7.8		$	25.1		$	(32.8	)	$	(139.5	)	$	(135.2	)
Other comprehensive income (loss) before reclassifications	(9.0		)	33.2			18.6			0.9			(47.0		)	(3.3		)
Amounts reclassified from accumulated other comprehensive income (loss)	9.9			(50.6		)	(1.8		)	—			—			(42.5		)
Net current period other comprehensive income (loss)	0.9			(17.4		)	16.8			0.9			(47.0		)	(45.8		)
Balance, June 30, 2020	$	5.1		$	(9.6	)	$	41.9		$	(31.9	)	$	(186.5	)	$	(181.0	)



(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 Hedge			Unfunded Status of Postretirement Benefit Plans, Net of Tax			Currency Translation Adjustments			Total
Balance, December 31, 2018	$	(4.0	)	$	34.7		$	3.5		$	(31.3	)	$	(243.3	)	$	(240.4	)
Other comprehensive income (loss) before reclassifications	11.0			22.3			30.1			0.7			(28.1		)	36.0
Amounts reclassified from accumulated other comprehensive income (loss)	(0.8		)	(43.3		)	(4.4		)	—			—			(48.5		)
Net current period other comprehensive income (loss)	10.2			(21.0		)	25.7			0.7			(28.1		)	(12.5		)
Balance, June 30, 2019	$	6.2		$	13.7		$	29.2		$	(30.6	)	$	(271.4	)	$	(252.9	)

Reclassification out of Accumulated Other Comprehensive Income

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



(In millions)	Income Statement Location	Amounts Reclassified from Accumulated Other Comprehensive Income
		For the Three Months Ended June 30,						For the Six Months Ended June 30,
		2020			2019			2020			2019
Gains (losses) on securities available for sale	Other income (expense)	$	3.9		$	0.7		$	(12.5	)	$	1.0
	Income tax benefit (expense)	(0.8		)	(0.1		)	2.6			(0.2		)

Gains (losses) on cash flow hedges	Revenues	23.7			29.8			50.7			44.6
	Operating expenses	—			(0.7		)	(0.1		)	(1.2		)
	Other income (expense)	0.1			—			0.2			0.1
	Income tax benefit (expense)	(0.1		)	(0.1		)	(0.2		)	(0.2		)

Gains (losses) on net investment hedge	Other income (expense)	0.9			2.2			1.8			4.4

Total reclassifications, net of tax		$	27.7		$	31.8		$	42.5		$	48.5

Business Acquisition (Details Textual) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($)	Jun. 30, 2019 Assets	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 07, 2019 USD ($) $ / shares
Business Acquisition [Line Items]
Acquired in-process research and development			$ 0.0	$ 0.0	$ 75.0	$ 0.0
Clinical Assets Acquired \| Assets		2
BIIB118
Business Acquisition [Line Items]
Acquired in-process research and development	$ 75.0
Estimated additional payments upon achievement of development and commercial milestones	$ 635.0
Nightstar
Business Acquisition [Line Items]
Price per share \| $ / shares							$ 25.50
Total transaction value				847.6
Payments for pre-combination equity compensation				4.6
In-process research and development							$ 700.0
Selling, general and administrative \| Nightstar
Business Acquisition [Line Items]
Fair value of post-combination equity compensation				18.4
Research and development \| Nightstar
Business Acquisition [Line Items]
Fair value of post-combination equity compensation				7.8
Post-acquisition equity compensation \| Nightstar
Business Acquisition [Line Items]
Fair value of post-combination equity compensation				$ 26.2

Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2020	Jul. 21, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
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	2020
Document Fiscal Period Focus	Q2
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
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		158,313,471

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Summary of assets and liabilities recorded at fair value



As of June 30, 2020 (In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	1,869.6	$	—	$	1,869.6	$	—
Marketable debt securities:
Corporate debt securities	1,790.2		—		1,790.2		—
Government securities	966.8		—		966.8		—
Mortgage and other asset backed securities	108.5		—		108.5		—
Marketable equity securities	527.0		344.3		182.7		—
Derivative contracts	59.9		—		59.9		—
Plan assets for deferred compensation	27.7		—		27.7		—
Total	$	5,349.7	$	344.3	$	5,005.4	$	—
Liabilities:
Derivative contracts	$	14.3	$	—	$	14.3	$	—
Contingent consideration obligations	351.6		—		—		351.6
Total	$	365.9	$	—	$	14.3	$	351.6



As of December 31, 2019 (In millions)	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,541.1	$	—	$	2,541.1	$	—
Marketable debt securities:
Corporate debt securities	1,695.1		—		1,695.1		—
Government securities	1,013.9		—		1,013.9		—
Mortgage and other asset backed securities	261.3		—		261.3		—
Marketable equity securities	337.5		7.9		329.6		—
Derivative contracts	43.8		—		43.8		—
Plan assets for deferred compensation	27.7		—		27.7		—
Total	$	5,920.4	$	7.9	$	5,912.5	$	—
Liabilities:
Derivative contracts	$	8.3	$	—	$	8.3	$	—
Contingent consideration obligations	346.1		—		—		346.1
Total	$	354.4	$	—	$	8.3	$	346.1

Summary of fair and carrying value of debt instruments

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



	As of June 30, 2020				As of December 31, 2019
(In millions)	Fair Value		Carrying Value		Fair Value		Carrying Value
2.900% Senior Notes due September 15, 2020⁽¹⁾	$	—	$	—	$	1,509.6	$	1,495.8
3.625% Senior Notes due September 15, 2022	1,061.0		997.3		1,038.9		996.6
4.050% Senior Notes due September 15, 2025	1,994.1		1,740.3		1,897.2		1,739.5
2.250% Senior Notes due May 1, 2030	1,514.1		1,490.7		—		—
5.200% Senior Notes due September 15, 2045	2,247.1		1,723.2		2,107.9		1,722.9
3.150% Senior Notes due May 1, 2050	1,441.3		1,472.3		—		—
Total	$	8,257.6	$	7,423.8	$	6,553.6	$	5,954.8

Fair value of contingent consideration obligations

The following table provides a roll forward of the fair values of our contingent consideration obligations, which includes Level 3 measurements:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Fair value, beginning of period	$	341.6	$	421.3		$	346.1	$	409.8
Changes in fair value	10.0		(20.0		)	5.5		(8.5		)
Payments	—		—			—		—
Fair value, end of period	$	351.6	$	401.3		$	351.6	$	401.3

Earnings per Share

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Earnings per Share

Basic and diluted earnings per share are calculated as follows:



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Numerator:
Net income attributable to Biogen Inc.	$	1,542.1	$	1,494.1	$	2,941.2	$	2,902.9
Denominator:
Weighted average number of common shares outstanding	160.6		190.3		166.7		193.4
Effect of dilutive securities:
Time-vested restricted stock units	0.1		0.1		0.1		0.2
Market stock units	0.1		—		0.1		0.1
Performance stock units settled in stock	0.1		—		0.1		—
Dilutive potential common shares	0.3		0.1		0.3		0.3
Shares used in calculating diluted earnings per share	160.9		190.4		167.0		193.7

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

Other Consolidated Financial Statement (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Gain (loss) on investments, net	$ 106.8	$ (173.4)	$ 29.5	$ 203.0
Other long-term liabilities	1,475.4		1,475.4		$ 1,348.9
Accrued income taxes	743.2		743.2		803.3
Net gains recognized on the increase in fair value of equity securities	102.9	(131.3)	42.0	159.5
Proceeds from sale of available-for-sale securities, equity			0.5	$ 309.7
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense			$ 635.0		$ 697.0
Ionis
Class of Stock [Line Items]
Net gains recognized on the increase in fair value of equity securities	67.2
Proceeds from sale of available-for-sale securities, equity		$ 203.0
Sangamo
Class of Stock [Line Items]
Net gains recognized on the increase in fair value of equity securities	$ 40.9

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income attributable to Biogen Inc.	$ 1,542.1	$ 1,494.1	$ 2,941.2	$ 2,902.9
Other comprehensive income:
Unrealized gains (losses) on securities available for sale, net of tax	8.7	3.3	0.9	10.2
Unrealized gains (losses) on cash flow hedges, net of tax	(51.2)	(37.9)	(17.4)	(21.0)
Gains (losses) on net investment hedges	(6.2)	11.7	16.8	25.7
Unrealized gains (losses) on pension benefit obligation, net of tax	0.1	0.1	0.9	0.7
Currency translation adjustment	16.9	(10.3)	(47.0)	(28.1)
Total other comprehensive income (loss), net of tax	(31.7)	(33.1)	(45.8)	(12.5)
Comprehensive income	1,510.4	1,461.0	2,895.4	2,890.4
Comprehensive income (loss) attributable to noncontrolling interests, net of tax	65.5	(0.4)	59.6	(0.4)
Comprehensive income attributable to Biogen Inc.	$ 1,575.9	$ 1,460.6	$ 2,955.0	$ 2,890.0

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	2018 Share Repurchase Program	2018 Share Repurchase Program Common stock	2018 Share Repurchase Program Additional paid-in capital	2018 Share Repurchase Program Retained earnings	2018 Share Repurchase Program Treasury stock	2018 Share Repurchase Program Parent	2019 Share Repurchase Program	2019 Share Repurchase Program Common stock	2019 Share Repurchase Program Additional paid-in capital	2019 Share Repurchase Program Retained earnings	2019 Share Repurchase Program Treasury stock	2019 Share Repurchase Program Parent	December 2019 Share Repurchase Program	December 2019 Share Repurchase Program Common stock	December 2019 Share Repurchase Program Additional paid-in capital	December 2019 Share Repurchase Program Retained earnings	December 2019 Share Repurchase Program Treasury stock	December 2019 Share Repurchase Program Parent
Beginning balance, shares at Dec. 31, 2018		0.0	(221.0)				(23.8)
Beginning balance at Dec. 31, 2018	$ 13,031.6	$ 0.0	$ 0.1	$ 0.0	$ (240.4)	$ 16,257.0	$ (2,977.1)	$ 13,039.6	$ (8.0)
Net income	2,902.9					2,902.9		2,902.9
Other comprehensive income (loss), net of tax	(12.9)				(12.5)			(12.5)	(0.4)
Noncontrolling interest, increase (decrease) other	4.3							0.0	4.3
Repurchase of common stock, at cost, shares														(8.9)						(3.9)
Repurchase of common stock, at cost										$ (2,147.4)				$ (2,147.4)	$ (2,147.4)	$ (909.9)				$ (909.9)	$ (909.9)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares											(8.9)			(8.9)			(3.9)			(3.9)
Retirement of common stock pursuant to Share Repurchase Progams, at cost										0.0	$ 0.0	$ (110.5)	$ (2,036.9)	$ 2,147.4	0.0			$ (19.7)	$ (890.2)	$ 909.9
Issuance of common stock under stock option and stock purchase plans, shares			0.1
Issuance of common stock under stock option and stock purchase plans	26.2		$ 0.0	26.2				26.2
Issuance of common stock under award plan, shares			0.3
Issuance of common stock under stock award plan	(50.0)		$ 0.0	0.0		(50.0)		(50.0)
Compensation related to share-based payments	104.0			104.0		0.0		104.0
Ending balance at Jun. 30, 2019	12,948.8	$ 0.0	$ 0.1	0.0	(252.9)	16,182.8	$ (2,977.1)	12,952.9	(4.1)
Ending balance, shares at Jun. 30, 2019		0.0	(208.6)				(23.8)
Beginning balance, shares at Mar. 31, 2019		0.0	(219.0)				(23.8)
Beginning balance at Mar. 31, 2019	13,822.0	$ 0.0	$ 0.1	0.0	(219.8)	17,026.7	$ (2,977.1)	13,829.9	(7.9)
Net income	1,494.1					1,494.1		1,494.1
Other comprehensive income (loss), net of tax	(33.5)				(33.1)			(33.1)	(0.4)
Noncontrolling interest, increase (decrease) other	4.2							0.0	4.2
Repurchase of common stock, at cost, shares														(6.5)						(3.9)
Repurchase of common stock, at cost										(1,491.6)				$ (1,491.6)	(1,491.6)	$ (909.9)				$ (909.9)	(909.9)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares											(6.5)			(6.5)			(3.9)			(3.9)
Retirement of common stock pursuant to Share Repurchase Progams, at cost										$ 0.0	$ 0.0	$ (44.9)	$ (1,446.7)	$ 1,491.6	$ 0.0			(19.7)	(890.2)	$ 909.9
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	9.6		$ 0.0	9.6				9.6
Issuance of common stock under award plan, shares			0.0
Issuance of common stock under stock award plan	(1.1)		$ 0.0	0.0		(1.1)		(1.1)
Compensation related to share-based payments	55.0			55.0		0.0		55.0
Ending balance at Jun. 30, 2019	12,948.8	$ 0.0	$ 0.1	0.0	(252.9)	16,182.8	$ (2,977.1)	12,952.9	(4.1)
Ending balance, shares at Jun. 30, 2019		0.0	(208.6)				(23.8)
Beginning balance, shares at Dec. 31, 2019		0.0	(198.0)				(23.8)
Beginning balance at Dec. 31, 2019	13,339.1	$ 0.0	$ 0.1	0.0	(135.2)	16,455.4	$ (2,977.1)	13,343.2	(4.1)
Net income	2,999.0					2,941.2		2,941.2	57.8
Other comprehensive income (loss), net of tax	(44.0)				(45.8)			(45.8)	1.8
Noncontrolling interest, increase (decrease) other	(75.0)								(75.0)
Repurchase of common stock, at cost, shares																(4.1)				(4.1)		(12.2)				(12.2)
Repurchase of common stock, at cost																$ (1,279.1)				$ (1,279.1)	$ (1,279.1)	$ (3,750.0)				$ (3,750.0)	$ (3,750.0)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares																	(4.1)			(4.1)			(12.2)			(12.2)
Retirement of common stock pursuant to Share Repurchase Progams, at cost																$ 0.0		$ (71.0)	$ (1,208.1)	$ 1,279.1		$ 0.0		$ (76.2)	$ (3,673.8)	$ 3,750.0
Issuance of common stock under stock option and stock purchase plans, shares			0.1
Issuance of common stock under stock option and stock purchase plans	29.1		$ 0.0	29.1				29.1
Issuance of common stock under award plan, shares			0.3
Issuance of common stock under stock award plan	(48.0)		$ 0.0	0.0		(48.0)		(48.0)
Compensation related to share-based payments	118.8			118.8				118.8
Other	(0.7)			(0.7)				(0.7)
Ending balance at Jun. 30, 2020	11,289.2	$ 0.0	$ 0.1	0.0	(181.0)	14,466.7	$ (2,977.1)	11,308.7	(19.5)
Ending balance, shares at Jun. 30, 2020		0.0	(182.1)				(23.8)
Beginning balance, shares at Mar. 31, 2020		0.0	(191.1)				(23.8)
Beginning balance at Mar. 31, 2020	12,536.9	$ 0.0	$ 0.1	0.1	(149.3)	15,673.1	$ (2,977.1)	12,546.9	(10.0)
Net income	1,606.5					1,542.1		1,542.1	64.4
Other comprehensive income (loss), net of tax	(30.6)				(31.7)			(31.7)	1.1
Noncontrolling interest, increase (decrease) other	(75.0)							0.0	(75.0)
Repurchase of common stock, at cost, shares																						(9.0)				(9.0)
Repurchase of common stock, at cost																						$ (2,808.9)				$ (2,808.9)	(2,808.9)
Retirement of common stock pursuant to Share Repurchase Programs, at cost, shares																							(9.0)			(9.0)
Retirement of common stock pursuant to Share Repurchase Progams, at cost																						$ 0.0	$ 0.0	$ (60.7)	$ (2,748.2)	$ 2,808.9	$ 0.0
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	11.1		$ 0.0	11.1				11.1
Issuance of common stock under award plan, shares			0.0
Issuance of common stock under stock award plan	(0.3)		$ 0.0	0.0		(0.3)		(0.3)
Compensation related to share-based payments	49.5			49.5				49.5
Other	0.0			0.0				0.0
Ending balance at Jun. 30, 2020	$ 11,289.2	$ 0.0	$ 0.1	$ 0.0	$ (181.0)	$ 14,466.7	$ (2,977.1)	$ 11,308.7	$ (19.5)
Ending balance, shares at Jun. 30, 2020		0.0	(182.1)				(23.8)

Other Consolidated Financial Statement Detail (Tables)

6 Months Ended

Jun. 30, 2020

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Interest income	$	7.6		$	29.1		$	32.0		$	60.3
Interest expense	(66.0		)	(47.7		)	(110.3		)	(95.6		)
Gain (loss) on investments, net	106.8			(173.4		)	29.5			203.0
Foreign exchange gains (losses), net	10.4			1.7			(8.5		)	(0.5		)
Other, net	4.2			(7.1		)	(0.2		)	(7.3		)
Total other income (expense), net	$	63.0		$	(197.4	)	$	(57.5	)	$	159.9

Gain (loss) on investments in equity securities

The following table summarizes our gain (loss) on investments, net that relates to our equity securities held as of June 30, 2020 and 2019:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Net gains (losses) recognized during the period on equity securities	$	102.9	$	(174.2	)	$	42.0	$	201.9
Less: Net gains (losses) recognized during the period on equity securities sold during the period	—		(42.9		)	—		42.4
Unrealized gains (losses) recognized during the period on equity securities	$	102.9	$	(131.3	)	$	42.0	$	159.5

Accrued expenses and other

Accrued expenses and other consists of the following:



(In millions)	As of June 30, 2020		As of December 31, 2019
Revenue-related reserves for discounts and allowances	$	951.3	$	1,001.1
Employee compensation and benefits	212.0		309.1
Royalties and licensing fees	203.0		220.9
Collaboration expenses	172.9		281.6
Current portion of contingent consideration obligations	149.1		148.4
Construction in progress	24.1		78.0
Other	774.1		726.7
Total accrued expenses and other	$	2,486.5	$	2,765.8

Investments in Variable Interest Entities	6 Months Ended
Investments in Variable Interest Entities	Jun. 30, 2020
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 SubOne AG (Neurimmune) for the development and commercialization of antibodies for the potential treatment of AD, including aducanumab (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 any product using such a licensed compound. 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% of the research and development costs incurred in support of the collaboration. In October 2017 we amended the terms of the Neurimmune Agreement and made a $150.0 million payment to Neurimmune in exchange for a 15% reduction in the previously negotiated royalty rates payable on products developed under the Neurimmune Agreement, including royalties payable on potential commercial sales of aducanumab. In May 2018 we made an additional $50.0 million payment to Neurimmune to further reduce the previously negotiated royalty rates payable on products developed under the Neurimmune Agreement, including royalties payable on potential commercial sales of aducanumab, by an additional 5%. Our royalty rates payable on products developed under the Neurimmune Agreement, including royalty rates payable on potential commercial sales of aducanumab, now range from the high single digits to sub-teens. As we consolidate the results of Neurimmune, we treated these payments as distributions and recognized them as charges to noncontrolling interests in the fourth quarter of 2017 and the second quarter of 2018, as applicable. Additionally, under the terms of the Neurimmune Agreement, we are required to pay Neurimmune a milestone payment of $75.0 million upon the regulatory filing with the FDA for approval of aducanumab and a milestone payment of $100.0 million if aducanumab is launched in the U.S. In July 2020 we and our collaboration partner Eisai announced that we completed the submission of a BLA to the FDA for the approval of aducanumab. As of June 30, 2020, we recorded accrued expenses of approximately $75.0 million related to this milestone payment as it was probable that the submission of the BLA would be completed and the milestone earned. This milestone payment is expected to be paid during the third quarter of 2020. For the three and six months ended June 30, 2020, we recognized net profit-sharing income of $33.8 million to reflect Eisai's 45% share of the $75.0 million milestone expense. We treated this milestone payment as a distribution and recognized it as a charge to noncontrolling interest for the three and six months ended June 30, 2020. For additional information on our collaboration arrangements with Eisai, please read Note 17, Collaborative and Other Relationships, to these condensed consolidated financial statements. Research and development costs for which we reimburse Neurimmune are reflected in research and development expense in our condensed consolidated statements of income. During the three and six months ended June 30, 2020 and 2019, amounts reimbursed were immaterial. 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. Under the Aducanumab Collaboration Agreement, Eisai had an option to share in the benefit and cost associated with the royalty reductions discussed above; however, Eisai did not elect to share in the benefit and cost with respect to either the October 2017 or May 2018 royalty reductions, which will impact the amount of profits (losses) on potential commercial sales of aducanumab to be shared with Eisai. For additional information on our collaboration arrangements with Eisai, please read Note 17, 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 June 30, 2020 and December 31, 2019, the carrying value of our investments in certain biotechnology companies representing potential unconsolidated variable interest entities totaled $22.4 million and $22.7 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 previously 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 2019 Form 10-K.

Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

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

The notional value of foreign currency forward contracts that were entered into to hedge forecasted revenues and operating expenses is summarized as follows:



	Notional Amount
(In millions)	As of June 30, 2020		As of December 31, 2019
Euro	$	2,477.3	$	1,892.4
British pound	125.1		—
Swiss franc	69.0		—
Japanese yen	53.9		—
Canadian dollar	48.1		—
Total foreign currency forward contracts	$	2,773.4	$	1,892.4

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 June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)						Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2020		2019			Location	2020			2019
Revenues	$	23.7	$	29.8		Revenues	$	(1.6	)	$	3.7
Operating expenses	—		(0.7		)	Operating expenses	(0.2		)	(0.3		)



For the Six Months Ended June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)							Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2020			2019			Location	2020			2019
Revenues	$	50.7		$	44.6		Revenues	$	7.7		$	7.4
Operating expenses	(0.1		)	(1.2		)	Operating expenses	(1.1		)	(1.2		)

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 hedge in our condensed consolidated financial statements:



For the Three Months Ended June 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	2020			2019		Location	2020		2019		Location	2020		2019
Gains (losses) on net investment hedge	$	(8.8	)	$	11.6	Gains (losses) on net investment hedge	$	3.5	$	2.3	Other income (expense)	$	0.8	$	2.2



For the Six Months Ended June 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	2020		2019		Location	2020		2019		Location	2020		2019
Gains (losses) on net investment hedge	$	15.4	$	23.4	Gains (losses) on net investment hedge	$	3.2	$	6.7	Other income (expense)	$	1.7	$	4.4

Summary of fair value and presentation of derivatives

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 June 30, 2020		As of December 31, 2019
Cash Flow Hedging Instruments:
Asset derivative instruments	Other current assets	$	32.2	$	33.8
	Investments and other assets	0.7		—
Liability derivative instruments	Accrued expenses and other	4.4		2.0
	Other long-term liabilities	9.0		1.7

Net Investment Hedging Instruments:
Asset derivative instruments	Other current assets	20.7		2.0

Fair Value Hedging Instruments:
Liability derivative instruments	Accrued expenses and other	—		2.3

Other Derivative Instruments:
Asset derivative instruments	Other current assets	6.4		8.0
Liability derivative instruments	Accrued expenses and other	0.8		2.4

Property, Plant and Equipment Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2020
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 $1,687.0 million and $1,590.9 million as of June 30, 2020 and December 31, 2019, respectively. For the three and six months ended June 30, 2020, depreciation expense totaled $51.3 million and $99.7 million, respectively, compared to $47.0 million and $99.9 million, respectively, in the prior year comparative periods. Solothurn, Switzerland Manufacturing Facility In order to support our drug development pipeline, we are building a large-scale biologics manufacturing facility in Solothurn, Switzerland. We expect this facility to be partially operational by the end of 2020. 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 June 30, 2020 and December 31, 2019, we had approximately $1.7 billion and $1.9 billion, respectively, capitalized as construction in progress related to this facility. For the six months ended June 30, 2020, we placed approximately $256.8 million of fixed assets in service related to this facility. As of June 30, 2020, we had contractual commitments of approximately $16.2 million outstanding related to the construction of this facility.

Litigation	6 Months Ended
Litigation	Jun. 30, 2020
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 2019 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 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, alleging that IMRALDI, the adalimumab biosimilar product of Samsung Bioepis UK Limited that Biogen has commercialized in Europe, infringes the French counterpart of European Patent No. 3 148 510 (the '510 Patent), which was issued in June 2018 and expires in May 2035. No hearing has been scheduled. In October 2018 Fresenius Kabi commenced preliminary injunction proceedings against Biogen (Denmark) Manufacturing ApS and Biogen Denmark A/S in Denmark's Maritime and Commercial High Court alleging infringement of Danish Utility Models. In June 2019 the Danish court denied Fresenius Kabi's request for a preliminary injunction and Fresenius Kabi has appealed that decision. In July 2020 the Danish Patent Board of Appeal revoked the Utility Models that were the subject of Fresenius Kabi’s October 2018 request for a preliminary injunction. Fresenius Kabi has not yet appealed those revocations. In June 2020 Fresenius Kabi commenced preliminary injunction proceedings against Biogen (Denmark) Manufacturing ApS and Biogen (Denmark) A/S in Denmark’s Maritime and Commercial High Court alleging infringement of another Danish Utility Model. No hearing has been scheduled in that action. In November 2018 Fresenius Kabi commenced infringement proceedings for damages and injunctive relief against Biogen Italia S.R.L. in the District Court of Milan relating to the Italian counterpart of the ‘510 Patent, and against Biogen GmbH in the Düsseldorf Regional Court relating to the German counterpart of the ‘510 Patent. In Italy, Fresenius Kabi has surrendered the Italian counterpart of the ‘510 Patent and has moved to dismiss its infringement action. A hearing in the proceeding in Germany has been set for April 2021. In July 2019 Gedeon Richter PLC (Gedeon Richter) commenced proceedings against Biogen GmbH in the Düsseldorf Regional Court alleging infringement of the German counterpart of European Patent No. 3 212 667 (the '667 Patent), which was issued in September 2018 and expires in October 2035, and seeking damages and injunctive relief. A hearing has been set for November 2020. In July 2019 Biogen Idec Ltd. (Biogen UK) and Samsung Bioepis UK Limited filed an action in the United Kingdom Patents Court to revoke the United Kingdom (U.K.) counterpart of the '667 Patent. In January 2020 the U.K. court revoked the patent. In August 2019 Biogen B.V. (Netherlands) and Samsung Bioepis UK Limited filed an action in the District Court of the Hague, Netherlands to revoke the Dutch counterpart of the '667 Patent. Gedeon Richter filed a separate action for infringement in the same court. A hearing was held in May 2020 on the request for revocation and the infringement action and a decision is pending. An estimate of the possible loss or range of loss in the pending IMRALDI patent litigation described above cannot be made at this time. Qui Tam Litigation In July 2015 a qui tam action filed by Michael Bawduniak on behalf of the U.S. and certain states was unsealed by the U.S. District Court for the District of Massachusetts. The action alleges sales and promotional activities in violation of the federal False Claims Act and state law counterparts and seeks single and treble damages, civil penalties, interest, attorneys’ fees and costs. No trial date has been set. The U.S. has not made an intervention decision. An estimate of the possible loss or range of loss cannot be made at this time. 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. Dispute with Jacobs Switzerland GmbH Jacobs Switzerland GmbH, the general contractor for the construction of our large-scale biologics manufacturing facility in Solothurn, Switzerland, claims approximately 31.0 million Swiss Francs (approximately $33.0 million) relating to construction costs. We dispute the claim. Other Matters Petition for Inter Partes Review In July 2018 Mylan filed a petition that was granted by the U.S. Patent Trial and Appeal Board (PTAB) for inter partes review of the '514 Patent, which covers treatment of MS with 480 mg of dimethyl fumarate per day as provided for in our TECFIDERA label. In February 2020 the PTAB issued a final written decision upholding the patentability of the ‘514 Patent and in April 2020 Mylan filed an appeal in the Federal Circuit, which is pending. Hatch-Waxman Act Litigation relating to TECFIDERA Orange-Book Listed Patents In 2017, 2018 and 2019 we filed patent infringement proceedings relating to TECFIDERA Orange-Book listed patents pursuant to the Drug Price Competition and Patent Term Restoration Act of 1984, commonly known as the Hatch-Waxman Act, against Accord Healthcare Inc., Alkem Laboratories Ltd., Amneal Pharmaceuticals LLC, Aurobindo Pharma U.S.A., Inc., Cipla Limited, Glenmark Pharmaceuticals Ltd., Graviti Pharmaceuticals Pvt. Ltd., Hetero USA, Inc., Lupin Atlantis Holdings SA, Macleods Pharmaceuticals, Ltd., MSN Laboratories Pvt. Ltd., Pharmathen S.A., Prinston Pharmaceutical Inc., Sandoz Inc., Sawai USA, Inc., Shilpa Medicare Limited, Slayback Pharma LLC, Torrent Pharmaceuticals Ltd., TWi Pharmaceuticals, Inc., Windlas Healthcare Pvt. Ltd. and Zydus Pharmaceuticals (USA) Inc. (the Delaware Defendants) in the U.S. District Court for the District of Delaware (the Delaware Court) and against Mylan in the West Virginia Court. The litigation against Aurobindo Pharma U.S.A., Inc., Glenmark Pharmaceuticals Ltd. and Sawai USA, Inc. was dismissed in the fourth quarter of 2019. A trial against the remaining Delaware Defendants was held in the Delaware Court in December 2019 and we are awaiting a decision. On June 22, 2020, the West Virginia Court entered judgment for Mylan that the asserted claims of the ‘514 Patent are invalid for lack of written description. We appealed the judgment on June 23, 2020, to the Federal Circuit and filed an emergency motion for an injunction pending resolution of the appeal. On June 30, 2020, the Federal Circuit entered an interim injunction enjoining Mylan from launching its generic version of TECFIDERA pending the Federal Circuit's consideration of our request for an injunction pending appeal. We have entered into settlement agreements with some of the Delaware Defendants and we now anticipate market entry of a generic product equivalent to TECFIDERA before the ‘514 Patent expires in February 2028. European Patent Office Oppositions In 2016 the European Patent Office (EPO) revoked our European Patent No. 2 137 537, which covers the treatment of MS with 480 mg of dimethyl fumarate as provided for in our TECFIDERA label. We have appealed to the Technical Boards of Appeal of the EPO and a hearing has been set for January 2021. In March 2018 the EPO revoked Forward Pharma’s European Patent No. 2 801 355, which expires in October 2025. Forward Pharma has filed an appeal to the Technical Boards of Appeal of the EPO and a hearing has been set for February 2021. TYSABRI Patent Revocation Matters In November 2017 Bioeq GMBH, affiliated with the Polpharma Group, brought an action in the Polish Patent Office seeking to revoke Polish Patent No. 215263 (the Polish '263 Patent), which corresponds to our European Patent No. 1 485 127 (the E.U. '127 Patent) and covers administration of natalizumab (TYSABRI) to treat MS. The Polish '263 Patent expires in February 2023. No hearing has been set in this matter. Swiss Pharma International AG, also affiliated with the Polpharma Group, filed actions in the District Court of the Hague, Netherlands (January 2016), the German Patents Court (March 2016) and the Commercial Court of Rome (November 2017) seeking to invalidate the Dutch, German and Italian counterparts, respectively, of the E.U. '127 Patent, which also cover administration of natalizumab (TYSABRI) to treat MS and expire in February 2023. The Dutch and German counterparts were ruled invalid. The decision in the Dutch action was affirmed on appeal and the German appeal has been withdrawn. No hearing has been set in the Italian action. '755 Patent Litigation In May 2010 Biogen MA Inc. (formerly Biogen Idec MA Inc.) filed a complaint in the U.S. District Court for the District of New Jersey alleging infringement by Bayer Healthcare Pharmaceuticals Inc. (Bayer) (manufacturer, marketer and seller of BETASERON and manufacturer of EXTAVIA), EMD Serono, Inc. (EMD Serono) (manufacturer, marketer and seller of REBIF), Pfizer (co-marketer of REBIF) and Novartis Pharmaceuticals Corp. (Novartis) (marketer and seller of EXTAVIA) of our U.S. Patent No. 7,588,755 (the '755 Patent), which claims, among other things, the use of interferon beta for immunomodulation. The complaint seeks monetary damages, including lost profits and royalties. Bayer, Pfizer, Novartis and EMD Serono all filed counterclaims seeking declaratory judgments of patent invalidity and non-infringement and seeking monetary relief in the form of costs and attorneys' fees. Bayer had previously filed a complaint against us in the same court, on May 27, 2010, seeking a declaratory judgment that it does not infringe the '755 Patent and that the '755 Patent is invalid, and seeking monetary relief in the form of attorneys' fees, costs and expenses. Bayer has also requested ex parte reexamination by the U.S. Patent and Trademark Office of Claim 1 of the ‘755 Patent, which request was granted in January 2020 and is pending. In September 2018 the trial court entered judgment against EMD Serono and Pfizer that the '755 Patent is infringed and valid and ordered a new trial on damages. EMD Serono and Pfizer filed an appeal in the U.S. Court of Appeals for the Federal Circuit, which is pending. The trial court has not yet scheduled the new damages trial or a trial against Bayer and Novartis. Annulment Proceeding in General Court of the European Union relating to TECFIDERA In October 2018 Pharmaceutical Works Polpharma SA (Polpharma) filed an application in the General Court of the European Union seeking to annul a decision of the European Medicines Agency (EMA) in which the EMA refused to validate Polpharma’s application to market a generic version of TECFIDERA on the grounds that TECFIDERA benefits from regulatory data protection (RDP). Polpharma disputes that TECFIDERA benefits from RDP. Biogen and the European Commission were granted leave to intervene in the case in support of the EMA and the case is pending. A hearing was held on July 13, 2020, and we are awaiting a decision. Government Matters We have learned that state and U.S. governmental authorities are investigating our sales and promotional practices and have received related subpoenas. We are cooperating with the investigation. We have received subpoenas and other requests from the U.S. government for documents and information relating to our relationship with non-profit organizations that assist patients taking drugs sold by Biogen and the government has challenged some of our contributions to these organizations. We have reached an agreement in principle with the government to resolve this matter. Tax Matter We previously reported that the State Treasury of Goias, Brazil issued tax assessments for the period 2013 through February 2018 relating to tax on the circulation of goods and totaling approximately $70.0 million including interest and penalties. In May 2020 the tax auditor recommended the cancellation of these assessments. We do not anticipate reporting on this matter further. 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.

Derivative Instruments

6 Months Ended

Jun. 30, 2020

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 revenues and operating expenses are recorded in currencies other than the U.S. dollar. The value of revenues and operating expenses measured in U.S. dollars is therefore subject to changes in foreign currency exchange rates. In order to mitigate these changes, we use foreign currency forward contracts to lock in exchange rates associated with a portion of our forecasted international revenues and operating expenses.

Foreign currency forward contracts in effect as of June 30, 2020 and December 31, 2019, had durations of 1 to 18 months and 1 to 15 months, respectively. 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 revenues when the sale of product in the currency being hedged is recognized and in operating expenses when the expense in the currency being hedged is recorded. We recognize all cash flow hedge reclassifications from accumulated other comprehensive income and fair value changes of excluded portions in the same line item in our condensed consolidated statements of income that has been impacted by the hedged item.

The notional value of foreign currency forward contracts that were entered into to hedge forecasted revenues and operating expenses is summarized as follows:



	Notional Amount
(In millions)	As of June 30, 2020		As of December 31, 2019
Euro	$	2,477.3	$	1,892.4
British pound	125.1		—
Swiss franc	69.0		—
Japanese yen	53.9		—
Canadian dollar	48.1		—
Total foreign currency forward contracts	$	2,773.4	$	1,892.4

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 losses of $16.8 million and net gains of $0.5 million as of June 30, 2020 and December 31, 2019, respectively. We expect the net losses of $16.8 million to be settled over the next 18 months, of which $7.9 million of these losses 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 revenues or operating expenses. 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 June 30, 2020 and December 31, 2019, 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 June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)						Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2020		2019			Location	2020			2019
Revenues	$	23.7	$	29.8		Revenues	$	(1.6	)	$	3.7
Operating expenses	—		(0.7		)	Operating expenses	(0.2		)	(0.3		)



For the Six Months Ended June 30,
Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions)							Net Gains/(Losses) Recognized in Operating Income (in millions)
Location	2020			2019			Location	2020			2019
Revenues	$	50.7		$	44.6		Revenues	$	7.7		$	7.4
Operating expenses	(0.1		)	(1.2		)	Operating expenses	(1.1		)	(1.2		)

Interest Rate Contracts - Hedging Instruments

We have entered into interest rate lock contracts or interest rate swap contracts on certain borrowing transactions to manage our exposure to interest rate changes and to reduce our overall cost of borrowing.

Interest Rate Swap Contracts

In connection with the issuance of our 2.90% Senior Notes due September 15, 2020, we entered into interest rate swaps with an aggregate notional amount of $675.0 million, which were originally set to expire on September 15, 2020. The interest rate swap contracts were designated as hedges of the fair value changes in our 2.90% Senior Notes attributable to changes in interest rates. The carrying value of our 2.90% Senior Notes as of December 31, 2019, included approximately $2.3 million related to changes in the fair value of these interest rate swap contracts. In May 2020 we settled our interest rate swap contracts, in conjunction with our early redemption of our 2.90% Senior Notes, resulting in a gain of approximately $3.3 million for the three and six months ended June 30, 2020, and was recorded as a component of interest expense in our condensed consolidated statements of income.

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% 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 is 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 have entered into foreign currency forward contracts. Foreign currency forward contracts in effect as of June 30, 2020, had remaining durations of four months. These contracts have been designated as net investment hedges. We recognize changes in the spot exchange rate 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 $13.9 million and net losses of $1.5 million as of June 30, 2020 and December 31, 2019, respectively. We exclude fair value changes related to the forward rate from our hedging relationship and will amortize 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 gains of $1.1 million and $2.9 million as of June 30, 2020 and December 31, 2019, respectively.

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



For the Three Months Ended June 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	2020			2019		Location	2020		2019		Location	2020		2019
Gains (losses) on net investment hedge	$	(8.8	)	$	11.6	Gains (losses) on net investment hedge	$	3.5	$	2.3	Other income (expense)	$	0.8	$	2.2



For the Six Months Ended June 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	2020		2019		Location	2020		2019		Location	2020		2019
Gains (losses) on net investment hedge	$	15.4	$	23.4	Gains (losses) on net investment hedge	$	3.2	$	6.7	Other income (expense)	$	1.7	$	4.4

For additional information on our collaboration arrangements with Samsung Bioepis, please read Note 17, 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 $999.3 million and $793.8 million as of June 30, 2020 and December 31, 2019, respectively. Net gains of $8.3 million and $5.9 million related to these contracts were recorded as a component of other income (expense), net for the three and six months ended June 30, 2020, respectively, compared to net gains of $0.9 million and net losses of $3.9 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.



(In millions)	Balance Sheet Location	As of June 30, 2020		As of December 31, 2019
Cash Flow Hedging Instruments:
Asset derivative instruments	Other current assets	$	32.2	$	33.8
	Investments and other assets	0.7		—
Liability derivative instruments	Accrued expenses and other	4.4		2.0
	Other long-term liabilities	9.0		1.7

Net Investment Hedging Instruments:
Asset derivative instruments	Other current assets	20.7		2.0

Fair Value Hedging Instruments:
Liability derivative instruments	Accrued expenses and other	—		2.3

Other Derivative Instruments:
Asset derivative instruments	Other current assets	6.4		8.0
Liability derivative instruments	Accrued expenses and other	0.8		2.4

Income Taxes

6 Months Ended

Jun. 30, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Coronavirus Aid, Relief and Economic Security Act

In response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Security Act (CARES Act) was signed into law in the U.S. in March 2020. The CARES Act lifts certain deduction limitations originally imposed by the Tax Cuts and Jobs Act of 2017 (2017 Tax Act). Corporate taxpayers may carryback net operating losses (NOLs) originating during 2018 through 2020 for up to five years, which was not previously allowed under the 2017 Tax Act. The CARES Act also eliminates the 80% of taxable income limitations by allowing corporate entities to fully utilize NOL carryforwards to offset taxable income in 2018, 2019 or 2020. Taxpayers may generally deduct interest up to the sum of 50% of adjusted taxable income plus business interest income (30% limit under the 2017 Tax Act) for tax years beginning January 1, 2019 and 2020. The CARES Act allows taxpayers with alternative minimum tax credits to claim a refund in 2020 for the entire amount of the credits instead of recovering the credits through refunds over a period of years, as originally enacted by the 2017 Tax Act.

In addition, the CARES Act raises the corporate charitable deduction limit to 25% of taxable income and makes qualified improvement property generally eligible for 15-year cost-recovery and 100% bonus depreciation. The enactment of the CARES Act did not result in any material adjustments to our income tax provision for the three and six months ended June 30, 2020, or to our net deferred tax assets as of June 30, 2020.

TECFIDERA

On June 22, 2020, the U.S. District Court for the Northern District of West Virginia (the West Virginia Court)

entered judgment for Mylan Pharmaceuticals, Inc. (Mylan) that the asserted claims of our U.S. Patent No. 8,399,514

(the '514 Patent) are invalid for lack of written description. The '514 Patent covers treatment of MS with 480 mg of

dimethyl fumarate per day as provided for in our TECFIDERA label, and the litigation was filed pursuant to the Drug

Competition and Patent Term Restoration Act of 1984, commonly known as the Hatch-Waxman Act. We appealed the

judgment on June 23, 2020, to the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) and filed an

emergency motion for an injunction pending resolution of the appeal. On June 30, 2020, the Federal Circuit entered

an interim injunction enjoining Mylan from launching its generic version of TECFIDERA pending the Federal Circuit's

consideration of our request for an injunction pending appeal. In the event that our request for an injunction pending appeal is denied, generic entry could occur during the appeal. The commercialization of a generic version of TECFIDERA would have an adverse impact on our TECFIDERA sales and our results of operations.

As of June 30, 2020, we have assessed the realizability of our deferred tax assets that are dependent on future expected sales of TECFIDERA in the U.S. and reduced the value of certain deferred tax assets by approximately $1,324.0 million and reduced the value of deferred tax liabilities associated with global intangible low-taxed income (GILTI) and tax credits by approximately $1,268.0 million. For the three and six months ended June 30, 2020, the income tax expense associated with these reductions was approximately $56.0 million. For additional information, please read Note 19, Litigation, to these condensed consolidated financial statements.

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 June 30,				For the Six Months Ended June 30,
	2020		2019		2020		2019
Statutory rate	21.0	%	21.0	%	21.0	%	21.0	%
State taxes	0.4		0.9		0.5		0.6
Taxes on foreign earnings	(3.4	)	(4.6	)	(3.7	)	(4.6	)
Tax credits	(1.0	)	(0.9	)	(1.0	)	(0.8	)
Purchased intangible assets	0.2		0.4		0.2		0.4
Divestiture of Denmark manufacturing operations	—		—		—		2.2
Internal reorganization of certain intellectual property rights	—		(5.0	)	—		(2.4	)
TECFIDERA impairment	2.7		—		1.5		—
GILTI	1.5		1.4		1.1		1.7
Other permanent items	0.1		0.4		0.1		0.3
Other	0.4		0.5		0.1		0.1
Effective tax rate	21.9	%	14.1	%	19.8	%	18.5	%

Changes in Tax Rate

For the three months ended June 30, 2020, compared to the same period in 2019, the increase in our effective tax rate was primarily due to an internal reorganization of certain intellectual property rights related to the intercompany sale of the intellectual property in 2019 and the $56.0 million income tax expense related to the establishment of a valuation allowance against certain deferred tax assets, the realization of which is dependent on future sales of TECFIDERA in the U.S., as discussed above.

For the six months ended June 30, 2020, compared to the same period in 2019, the increase in our effective tax rate was primarily due to the impacts of the valuation allowance described above and the internal reorganization of certain intellectual property rights, partially offset by the $61.3 million tax expense recognized in 2019 related to the planned divestiture of our Hillerød, Denmark manufacturing operations. Although we recognized a loss on the divestiture of our Hillerød, Denmark manufacturing operations, the divestiture required us to write off certain deferred tax assets and resulted in a taxable gain in certain jurisdictions.

As a result of the internal reorganization of certain intellectual property rights, we recorded a deferred tax asset of $856.7 million and a deferred tax liability of $685.3 million as of June 30, 2019.

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 2013 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.

In April 2020 we became aware of a withholding tax regulation that could be interpreted to apply to certain of our previous transactions. As of June 30, 2020, we have recorded an immaterial reserve reflecting this uncertain tax position.

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 $75.0 million in the next 12 months as a result of various audit closures, settlements and expiration of the statute of limitations.

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 2,384.9	$ 2,913.7
Marketable securities	1,942.7	1,562.2
Accounts receivable, net	2,133.6	1,880.5
Due from anti-CD20 therapeutic programs	441.1	590.2
Inventory	952.7	804.2
Other current assets	638.8	631.0
Total current assets	8,493.8	8,381.8
Marketable securities	922.8	1,408.1
Property, plant and equipment, net	3,330.7	3,247.3
Operating lease assets	436.2	427.0
Intangible assets, net	3,383.8	3,527.4
Goodwill	5,751.0	5,757.8
Deferred tax asset	1,710.2	3,232.1
Investments and other assets	1,483.3	1,252.8
Total assets	25,511.8	27,234.3
Current liabilities:
Current portion of notes payable	0.0	1,495.8
Taxes payable	576.7	71.4
Accounts payable	383.9	530.8
Accrued expenses and other	2,486.5	2,765.8
Total current liabilities	3,447.1	4,863.8
Notes payable	7,423.8	4,459.0
Deferred tax liability	1,461.5	2,810.8
Long-term operating lease liabilities	414.8	412.7
Other long-term liabilities	1,475.4	1,348.9
Total liabilities	14,222.6	13,895.2
Commitments and contingencies
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	0.0
Accumulated other comprehensive loss	(181.0)	(135.2)
Retained earnings	14,466.7	16,455.4
Treasury stock, at cost	(2,977.1)	(2,977.1)
Total Biogen Inc. shareholders’ equity	11,308.7	13,343.2
Noncontrolling interests	(19.5)	(4.1)
Total equity	11,289.2	13,339.1
Total liabilities and equity	$ 25,511.8	$ 27,234.3

Fair Value Measurements Fair Value Measurements - Contingent Consideration (Details) - Discount rate	Jun. 30, 2020
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input	0.0083
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input	0.0118
Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input	0.0092

Income Taxes (Details)	3 Months Ended		6 Months Ended
Income Taxes (Details)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
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	0.40%	0.90%	0.50%	0.60%
Taxes on foreign earnings	(3.40%)	(4.60%)	(3.70%)	(4.60%)
Credits and net operating loss utilization	(1.00%)	(0.90%)	(1.00%)	(0.80%)
Purchased intangible assets	0.20%	0.40%	0.20%	0.40%
Denmark assets held for sale	0.00%	0.00%	0.00%	2.20%
Internal reorganization of certain intellectual property rights	0.00%	(5.00%)	0.00%	(2.40%)
TECFIDERA impairment	2.70%	0.00%	1.50%	0.00%
GILTI	1.50%	1.40%	1.10%	1.70%
Permanent items	0.10%	0.40%	0.10%	0.30%
Other	0.40%	0.50%	0.10%	0.10%
Effective tax rate	21.90%	14.10%	19.80%	18.50%

Reclassification out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Nonoperating Income (Expense)	$ 63.0	$ (197.4)	$ (57.5)	$ 159.9
Income Tax Expense (Benefit)	446.1	248.1	738.2	670.6
Product revenues	(3,681.6)	(3,616.7)	(7,215.9)	(7,106.5)
Net income attributable to Biogen Inc.	1,542.1	1,494.1	2,941.2	2,902.9
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.	27.7	31.8	42.5	48.5
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]
Nonoperating Income (Expense)	3.9	0.7	(12.5)	1.0
Income Tax Expense (Benefit)	(0.8)	(0.1)	2.6	(0.2)
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]
Nonoperating Income (Expense)	0.1	0.0	0.2	0.1
Income Tax Expense (Benefit)	(0.1)	(0.1)	(0.2)	(0.2)
Product revenues	(23.7)	29.8	(50.7)	44.6
Operating Expenses	0.0	(0.7)	(0.1)	1.2
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]
Nonoperating Income (Expense)	$ 0.9	$ 2.2	$ 1.8	$ 4.4

Equity

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Equity

Share Repurchases

In December 2019 our Board of Directors authorized a program to repurchase up to $5.0 billion of our common stock (December 2019 Share Repurchase Program). Our December 2019 Share Repurchase Program does not have an expiration date. All shares repurchased under our December 2019 Share Repurchase Program will be retired. Under our December 2019 Share Repurchase Program, we repurchased and retired approximately 9.0 million and 12.2 million shares of our common stock at a cost of approximately $2.8 billion and $3.7 billion during the three and six months ended June 30, 2020, respectively. Approximately $1.3 billion remained available under our December 2019 Share Repurchase Program as of June 30, 2020.

In March 2019 our Board of Directors authorized a program to repurchase up to $5.0 billion of our common stock (March 2019 Share Repurchase Program), which was completed as of March 31, 2020. All shares repurchased under our March 2019 Share Repurchase Program were retired. Under our March 2019 Share Repurchase Program, we repurchased and retired approximately 4.1 million shares of our common stock at a cost of approximately $1.3 billion during the six months ended June 30, 2020.

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 Hedge			Unfunded Status of Postretirement Benefit Plans, Net of Tax			Currency Translation Adjustments			Total
Balance, December 31, 2019	$	4.2		$	7.8		$	25.1		$	(32.8	)	$	(139.5	)	$	(135.2	)
Other comprehensive income (loss) before reclassifications	(9.0		)	33.2			18.6			0.9			(47.0		)	(3.3		)
Amounts reclassified from accumulated other comprehensive income (loss)	9.9			(50.6		)	(1.8		)	—			—			(42.5		)
Net current period other comprehensive income (loss)	0.9			(17.4		)	16.8			0.9			(47.0		)	(45.8		)
Balance, June 30, 2020	$	5.1		$	(9.6	)	$	41.9		$	(31.9	)	$	(186.5	)	$	(181.0	)



(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 Hedge			Unfunded Status of Postretirement Benefit Plans, Net of Tax			Currency Translation Adjustments			Total
Balance, December 31, 2018	$	(4.0	)	$	34.7		$	3.5		$	(31.3	)	$	(243.3	)	$	(240.4	)
Other comprehensive income (loss) before reclassifications	11.0			22.3			30.1			0.7			(28.1		)	36.0
Amounts reclassified from accumulated other comprehensive income (loss)	(0.8		)	(43.3		)	(4.4		)	—			—			(48.5		)
Net current period other comprehensive income (loss)	10.2			(21.0		)	25.7			0.7			(28.1		)	(12.5		)
Balance, June 30, 2019	$	6.2		$	13.7		$	29.2		$	(30.6	)	$	(271.4	)	$	(252.9	)

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



(In millions)	Income Statement Location	Amounts Reclassified from Accumulated Other Comprehensive Income
		For the Three Months Ended June 30,						For the Six Months Ended June 30,
		2020			2019			2020			2019
Gains (losses) on securities available for sale	Other income (expense)	$	3.9		$	0.7		$	(12.5	)	$	1.0
	Income tax benefit (expense)	(0.8		)	(0.1		)	2.6			(0.2		)

Gains (losses) on cash flow hedges	Revenues	23.7			29.8			50.7			44.6
	Operating expenses	—			(0.7		)	(0.1		)	(1.2		)
	Other income (expense)	0.1			—			0.2			0.1
	Income tax benefit (expense)	(0.1		)	(0.1		)	(0.2		)	(0.2		)

Gains (losses) on net investment hedge	Other income (expense)	0.9			2.2			1.8			4.4

Total reclassifications, net of tax		$	27.7		$	31.8		$	42.5		$	48.5

Financial Instruments (Details 1) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 2,859.1	$ 2,965.0
Gross unrealized gains	7.3	6.0
Gross unrealized losses	(0.9)	(0.7)
Fair value	2,865.5	2,970.3
Marketable equity securities, fair value	2,865.5	2,970.3
Corporate debt securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	1,282.5	1,057.2
Gross unrealized gains	1.5	1.0
Gross unrealized losses	(0.1)	0.0
Fair value	1,283.9	1,058.2
Corporate debt securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	502.8	633.9
Gross unrealized gains	3.8	3.0
Gross unrealized losses	(0.3)	0.0
Fair value	506.3	636.9
Government securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	657.7	502.9
Gross unrealized gains	0.5	0.4
Gross unrealized losses	0.0	0.0
Fair value	658.2	503.3
Government securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	307.9	510.1
Gross unrealized gains	0.8	0.8
Gross unrealized losses	(0.1)	(0.3)
Fair value	308.6	510.6
Mortgage and other asset backed securities Current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0.6	0.7
Gross unrealized gains	0.0	0.0
Gross unrealized losses	0.0	0.0
Fair value	0.6	0.7
Mortgage and other asset backed securities Non-current
Debt Securities, Available-for-sale [Line Items]
Amortized cost	107.6	260.2
Gross unrealized gains	0.7	0.8
Gross unrealized losses	(0.4)	(0.4)
Fair value	107.9	260.6
Marketable equity securities
Debt Securities, Available-for-sale [Line Items]
Marketable equity securities, amortized cost	428.0	218.4
Marketable equity securities, gross unrealized gains	114.6	132.1
Marketable equity securities, gross unrealized losses	(15.6)	(13.0)
Marketable equity securities, fair value	$ 527.0	$ 337.5

Revenues (Tables)

6 Months Ended

Jun. 30, 2020

Revenue from Contract with Customer [Abstract]

Revenues by product

Revenues by product are summarized as follows:



	For the Three Months Ended June 30,
(In millions)	2020						2019
	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
Fumarate*	$	921.7	$	268.6	$	1,190.3	$	869.8	$	280.4	$	1,150.2
Interferon**	345.6		135.8		481.4		379.7		174.7		554.4
TYSABRI	244.1		187.9		432.0		264.3		211.0		475.3
FAMPYRA	—		23.0		23.0		—		24.1		24.1
Subtotal: MS product revenues	1,511.4		615.3		2,126.7		1,513.8		690.2		2,204.0

Spinal Muscular Atrophy:
SPINRAZA	210.3		284.3		494.6		230.6		257.6		488.2

Biosimilars:
BENEPALI	—		106.2		106.2		—		120.3		120.3
IMRALDI	—		44.8		44.8		—		47.3		47.3
FLIXABI	—		20.6		20.6		—		16.8		16.8
Subtotal: Biosimilar product revenues	—		171.6		171.6		—		184.4		184.4

Other:
FUMADERM	—		2.8		2.8		—		3.7		3.7
Total product revenues	$	1,721.7	$	1,074.0	$	2,795.7	$	1,744.4	$	1,135.9	$	2,880.3

*Fumarate includes TECFIDERA and VUMERITY. VUMERITY became commercially available in the U.S. in November 2019.

**Interferon includes AVONEX and PLEGRIDY.



	For the Six Months Ended June 30,
(In millions)	2020						2019
	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
Fumarate*	$	1,699.2	$	591.9	$	2,291.1	$	1,587.5	$	561.5	$	2,149.0
Interferon**	638.2		309.2		947.4		707.0		348.3		1,055.3
TYSABRI	521.8		432.6		954.4		509.3		426.4		935.7
FAMPYRA	—		51.3		51.3		—		47.0		47.0
Subtotal: MS product revenues	2,859.2		1,385.0		4,244.2		2,803.8		1,383.2		4,187.0

Spinal Muscular Atrophy:
SPINRAZA	445.7		613.9		1,059.6		453.9		552.8		1,006.7

Biosimilars:
BENEPALI	—		239.7		239.7		—		244.3		244.3
IMRALDI	—		106.4		106.4		—		83.0		83.0
FLIXABI	—		44.3		44.3		—		31.5		31.5
Subtotal: Biosimilar product revenues	—		390.4		390.4		—		358.8		358.8

Other:
FUMADERM	—		6.1		6.1		—		7.8		7.8
Total product revenues	$	3,304.9	$	2,395.4	$	5,700.3	$	3,257.7	$	2,302.6	$	5,560.3

*Fumarate includes TECFIDERA and VUMERITY. VUMERITY became commercially available in the U.S. in November 2019.

**Interferon includes AVONEX and PLEGRIDY.

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, as of December 31, 2019	$	131.1		$	1,027.3		$	40.5		$	1,198.9
Current provisions relating to sales in current year	387.5			1,624.2			9.9			2,021.6
Adjustments relating to prior years	(1.3		)	(25.7		)	0.7			(26.3		)
Payments/credits relating to sales in current year	(251.4		)	(1,018.7		)	—			(1,270.1		)
Payments/credits relating to sales in prior years	(126.5		)	(612.9		)	(10.0		)	(749.4		)
Balance, as of June 30, 2020	$	139.4		$	994.2		$	41.1		$	1,174.7

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 June 30, 2020		As of December 31, 2019
Reduction of accounts receivable, net	$	223.4	$	197.8
Component of accrued expenses and other	951.3		1,001.1
Total revenue-related reserves	$	1,174.7	$	1,198.9

Revenues from anti-CD20 therapeutic programs

Revenues from anti-CD20 therapeutic programs are summarized below. For the purposes of this footnote we refer to RITUXAN and RITUXAN HYCELA collectively as RITUXAN.



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Biogen’s share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	$	257.5	$	377.2	$	598.8	$	768.0
Other revenues from anti-CD20 therapeutic programs	220.8		199.2		399.9		325.8
Total revenues from anti-CD20 therapeutic programs	$	478.3	$	576.4	$	998.7	$	1,093.8

Other revenues

Other revenues are summarized as follows:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Revenues from collaborative and other relationships:
Profit (loss) earned under our 50% share of the co-promotion losses on ZINBRYTA in the U.S. with AbbVie Inc.	$	0.5	$	(0.1	)	$	0.7	$	(0.5	)
Revenues earned under our technical development agreement, manufacturing services agreements and royalty revenues on biosimilar products with Samsung Bioepis	4.5		52.2			8.2		77.0
Other royalty and corporate revenues:
Royalty	7.1		2.7			18.5		6.6
Other corporate	395.5		105.2			489.5		369.3
Total other revenues	$	407.6	$	160.0		$	516.9	$	452.4

Acquisitions	6 Months Ended
Acquisitions	Jun. 30, 2020
Business Combinations [Abstract]
Acquisitions	BIIB118 Acquisition In March 2020 we acquired BIIB118 (formerly known as PF-05251749), a novel CNS-penetrant small molecule inhibitor of casein kinase 1, for the potential treatment of patients with behavioral and neurological symptoms across various psychiatric and neurological diseases from Pfizer Inc. (Pfizer). We plan to develop the Phase 1 asset for the potential treatment of sundowning in AD and irregular sleep wake rhythm disorder in Parkinson’s disease. In connection with this acquisition, we made an upfront payment of $75.0 million to Pfizer, which was accounted for as an asset acquisition and recorded as acquired in-process research and development (IPR&D) in our condensed consolidated statements of income as BIIB118 has not yet reached technological feasibility. We may also pay Pfizer up to $635.0 million in potential additional development and commercialization milestone payments, as well as tiered royalties in the high single digits to sub-teens. Acquisition of Nightstar Therapeutics plc In June 2019 we completed our acquisition of all of the outstanding shares of Nightstar Therapeutics plc (NST), a clinical-stage gene therapy company focused on adeno-associated virus (AAV) treatments for inherited retinal disorders. As a result of this acquisition, we added two mid- to late-stage clinical assets, as well as preclinical programs, in ophthalmology. These assets include BIIB111 (timrepigene emparvovec), which is in Phase 3 development for the potential treatment of choroideremia, a rare, degenerative, X-linked inherited retinal disorder that leads to blindness and currently has no approved treatments, and BIIB112 (RPGR gene therapy), which is in Phase 2/3 development for the potential treatment of X-linked retinitis pigmentosa, which is a rare inherited retinal disease with no currently approved treatments. Under the terms of this acquisition, we paid NST shareholders $25.50 in cash for each issued and outstanding NST share, which totaled $847.6 million. In addition, we paid $4.6 million in cash for equity compensation, which is attributable to pre-combination services and was reflected as a component of the total purchase price paid. The fair value of equity compensation attributable to the post-combination service period was $26.2 million, of which $18.4 million was recognized as a charge to selling, general and administrative expense with the remaining $7.8 million as a charge to research and development expense in our condensed consolidated statements of income. These amounts were associated with the accelerated vesting of stock options previously granted to NST employees and were fully paid in cash as of June 30, 2019. We funded this acquisition through available cash and accounted for it as an acquisition of a business. We finalized purchase accounting for this acquisition in the fourth quarter of 2019. For additional information on our acquisition of NST, please read Note 2, Acquisitions, to our consolidated financial statements included in our 2019 Form 10-K.

Revenues Revenues

6 Months Ended

Jun. 30, 2020

Revenue from Contract with Customer [Abstract]

Revenues

Product Revenues

Revenues by product are summarized as follows:



	For the Three Months Ended June 30,
(In millions)	2020						2019
	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
Fumarate*	$	921.7	$	268.6	$	1,190.3	$	869.8	$	280.4	$	1,150.2
Interferon**	345.6		135.8		481.4		379.7		174.7		554.4
TYSABRI	244.1		187.9		432.0		264.3		211.0		475.3
FAMPYRA	—		23.0		23.0		—		24.1		24.1
Subtotal: MS product revenues	1,511.4		615.3		2,126.7		1,513.8		690.2		2,204.0

Spinal Muscular Atrophy:
SPINRAZA	210.3		284.3		494.6		230.6		257.6		488.2

Biosimilars:
BENEPALI	—		106.2		106.2		—		120.3		120.3
IMRALDI	—		44.8		44.8		—		47.3		47.3
FLIXABI	—		20.6		20.6		—		16.8		16.8
Subtotal: Biosimilar product revenues	—		171.6		171.6		—		184.4		184.4

Other:
FUMADERM	—		2.8		2.8		—		3.7		3.7
Total product revenues	$	1,721.7	$	1,074.0	$	2,795.7	$	1,744.4	$	1,135.9	$	2,880.3

*Fumarate includes TECFIDERA and VUMERITY. VUMERITY became commercially available in the U.S. in November 2019.

**Interferon includes AVONEX and PLEGRIDY.



	For the Six Months Ended June 30,
(In millions)	2020						2019
	United States		Rest of World		Total		United States		Rest of World		Total
Multiple Sclerosis (MS):
Fumarate*	$	1,699.2	$	591.9	$	2,291.1	$	1,587.5	$	561.5	$	2,149.0
Interferon**	638.2		309.2		947.4		707.0		348.3		1,055.3
TYSABRI	521.8		432.6		954.4		509.3		426.4		935.7
FAMPYRA	—		51.3		51.3		—		47.0		47.0
Subtotal: MS product revenues	2,859.2		1,385.0		4,244.2		2,803.8		1,383.2		4,187.0

Spinal Muscular Atrophy:
SPINRAZA	445.7		613.9		1,059.6		453.9		552.8		1,006.7

Biosimilars:
BENEPALI	—		239.7		239.7		—		244.3		244.3
IMRALDI	—		106.4		106.4		—		83.0		83.0
FLIXABI	—		44.3		44.3		—		31.5		31.5
Subtotal: Biosimilar product revenues	—		390.4		390.4		—		358.8		358.8

Other:
FUMADERM	—		6.1		6.1		—		7.8		7.8
Total product revenues	$	3,304.9	$	2,395.4	$	5,700.3	$	3,257.7	$	2,302.6	$	5,560.3

*Fumarate includes TECFIDERA and VUMERITY. VUMERITY became commercially available in the U.S. in November 2019.

**Interferon includes AVONEX and PLEGRIDY.

We recognized revenues from two wholesalers accounting for 31.7% and 17.9% of gross product revenues for the three months ended June 30, 2020, and 30.8% and 16.2% of gross product revenues for the six months ended June 30, 2020.

We recognized revenues from two wholesalers accounting for 30.5% and 18.2% of gross product revenues for the three months ended June 30, 2019, and 30.9% and 16.3% of gross product revenues for the six months ended June 30, 2019.

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



(In millions)	Discounts			Contractual Adjustments			Returns			Total
Balance, as of December 31, 2019	$	131.1		$	1,027.3		$	40.5		$	1,198.9
Current provisions relating to sales in current year	387.5			1,624.2			9.9			2,021.6
Adjustments relating to prior years	(1.3		)	(25.7		)	0.7			(26.3		)
Payments/credits relating to sales in current year	(251.4		)	(1,018.7		)	—			(1,270.1		)
Payments/credits relating to sales in prior years	(126.5		)	(612.9		)	(10.0		)	(749.4		)
Balance, as of June 30, 2020	$	139.4		$	994.2		$	41.1		$	1,174.7

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



(In millions)	As of June 30, 2020		As of December 31, 2019
Reduction of accounts receivable, net	$	223.4	$	197.8
Component of accrued expenses and other	951.3		1,001.1
Total revenue-related reserves	$	1,174.7	$	1,198.9

Revenues from Anti-CD20 Therapeutic Programs

Revenues from anti-CD20 therapeutic programs are summarized below. For the purposes of this footnote we refer to RITUXAN and RITUXAN HYCELA collectively as RITUXAN.



	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(In millions)	2020		2019		2020		2019
Biogen’s share of pre-tax profits in the U.S. for RITUXAN and GAZYVA	$	257.5	$	377.2	$	598.8	$	768.0
Other revenues from anti-CD20 therapeutic programs	220.8		199.2		399.9		325.8
Total revenues from anti-CD20 therapeutic programs	$	478.3	$	576.4	$	998.7	$	1,093.8

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 2019 Form 10-K.

Other Revenues

Other revenues are summarized as follows:



	For the Three Months Ended June 30,					For the Six Months Ended June 30,
(In millions)	2020		2019			2020		2019
Revenues from collaborative and other relationships:
Profit (loss) earned under our 50% share of the co-promotion losses on ZINBRYTA in the U.S. with AbbVie Inc.	$	0.5	$	(0.1	)	$	0.7	$	(0.5	)
Revenues earned under our technical development agreement, manufacturing services agreements and royalty revenues on biosimilar products with Samsung Bioepis	4.5		52.2			8.2		77.0
Other royalty and corporate revenues:
Royalty	7.1		2.7			18.5		6.6
Other corporate	395.5		105.2			489.5		369.3
Total other revenues	$	407.6	$	160.0		$	516.9	$	452.4

During the third quarter of 2019 we amended our agreement with a contract manufacturing customer, pursuant to which we licensed certain of our manufacturing-related intellectual property to the customer. In the second quarter of 2020 the customer received regulatory approval for its product that is being manufactured using certain of our manufacturing-related intellectual property. As a result, we are entitled to $500.0 million in a series of three payments. The first payment became due upon regulatory approval of such product and was received during the second quarter of 2020. Subsequent payments are due on the first and second anniversaries of the regulatory approval.

Other corporate revenues for the three and six months ended June 30, 2020, reflect $329.4 million related to the delivery of the license for certain of our manufacturing-related intellectual property under the amended agreement discussed above. We have allocated the remaining $170.6 million of the $500.0 million transaction price to the performance of manufacturing product supply services for the customer, which we expect to perform through 2026. The value allocated to the manufacturing services was based on expected demand for supply and the fair value of comparable manufacturing and development services.

Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 1,869.6	$ 2,541.1
Commercial paper
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	139.9	384.4
Overnight reverse repurchase agreements
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	247.7	368.8
Money market funds
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	1,363.7	1,628.5
Short-term debt securities
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 118.3	$ 159.4

Reserves for Discounts and Allowances (Details 1) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 1,198.9
Current Provisions Relating To Sales In Current Year	2,021.6
Adjustments Relating To Prior Years	(26.3)
Payments/Returns Relating To Sales in Current Year	(1,270.1)
Payments/Returns Relating To Sales in Prior Year	(749.4)
Ending Balance	1,174.7
Discounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	131.1
Current Provisions Relating To Sales In Current Year	387.5
Adjustments Relating To Prior Years	(1.3)
Payments/Returns Relating To Sales in Current Year	(251.4)
Payments/Returns Relating To Sales in Prior Year	(126.5)
Ending Balance	139.4
Contractual adjustments
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1,027.3
Current Provisions Relating To Sales In Current Year	1,624.2
Adjustments Relating To Prior Years	(25.7)
Payments/Returns Relating To Sales in Current Year	(1,018.7)
Payments/Returns Relating To Sales in Prior Year	(612.9)
Ending Balance	994.2
Returns
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	40.5
Current Provisions Relating To Sales In Current Year	9.9
Adjustments Relating To Prior Years	0.7
Payments/Returns Relating To Sales in Current Year	0.0
Payments/Returns Relating To Sales in Prior Year	(10.0)
Ending Balance	$ 41.1

Inventory (Tables)

6 Months Ended

Jun. 30, 2020

Inventory Disclosure [Abstract]

Components of inventory

The components of inventory are summarized as follows:



(In millions)	As of June 30, 2020		As of December 31, 2019
Raw materials	$	244.7	$	169.7
Work in process	509.1		460.0
Finished goods	198.9		174.5
Total inventory	$	952.7	$	804.2

Fair Value Measurements (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
Fair Value Measurements (Details Textual) - USD ($)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Business Acquisition, Contingent Consideration [Line Items]
Asset impairment charges	$ 0		$ 0
Contingent consideration obligations	202,500,000		202,500,000		$ 197,700,000
Contingent consideration impairment	(10,000,000.0)	$ 20,000,000.0	(5,500,000)	$ 8,500,000
Future payment	$ 0	$ 0	$ 0	$ 0
2.900% Senior Notes due 2020
Business Acquisition, Contingent Consideration [Line Items]
Senior notes interest rate	2.90%		2.90%
3.625% Senior Notes due 2022
Business Acquisition, Contingent Consideration [Line Items]
Senior notes interest rate	3.625%		3.625%
4.050% Senior Notes due 2025
Business Acquisition, Contingent Consideration [Line Items]
Senior notes interest rate	4.05%		4.05%
5.200% Senior Notes due 2045
Business Acquisition, Contingent Consideration [Line Items]
Senior notes interest rate	5.20%		5.20%

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Overview

Basis of presentation

Consolidation

Use of estimates

New accounting pronouncements

Credit Losses

Fair Value Measurements

Internal Use Software

Collaborative Arrangements

•


•	Adds unit-of-account guidance to ASC 808, Collaborative Arrangements, to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606; and


•	Precludes a company from presenting transactions with collaborative arrangement participants that are not directly related to sales to third parties with revenue recognized under ASC 606 if the collaborative arrangement participant is not a customer.

This standard became effective for us on January 1, 2020, and did not have a material impact on our condensed consolidated financial statements and related disclosures.

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 2,999.0	$ 2,902.9
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation, amortization and impairments	232.8	238.1
Acquired in-process research and development	75.0	0.0
Share-based compensation	115.8	98.0
Gain on interest rate swap	(3.3)	0.0
Contingent consideration	5.5	(8.5)
Loss on divestiture of Hillerød, Denmark manufacturing operations	0.0	113.2
Deferred income taxes	180.2	71.6
Unrealized (gain) loss on strategic investments	(39.7)	(199.2)
Other	85.3	91.1
Changes in operating assets and liabilities, net:
Accounts receivable	(268.8)	(2.9)
Due from anti-CD20 therapeutic programs	149.1	(30.6)
Inventory	(188.2)	108.7
Accrued expenses and other current liabilities	(441.4)	(216.1)
Income tax assets and liabilities	504.6	306.9
Other changes in operating assets and liabilities, net	9.9	(49.7)
Net cash flows provided by operating activities	3,415.8	3,423.5
Cash flows from investing activities:
Proceeds from sales and maturities of marketable securities	3,879.9	3,255.8
Purchases of marketable securities	(3,753.9)	(2,075.1)
Contingent consideration paid related to Fumapharm AG acquisition	0.0	(300.0)
Acquisition of Nightstar Therapeutics plc, net of cash acquired	0.0	(744.4)
Purchase of Sangamo Therapeutics, Inc. stock	(141.8)	0.0
Purchases of property, plant and equipment	(254.7)	(314.0)
Acquired in-process research and development	(75.0)	0.0
Acquisitions of intangible assets	(37.0)	0.0
Proceeds from settlement of net investment hedge	(7.8)	0.0
Proceeds from sales of strategic investments	0.5	309.7
Other	0.0	(4.0)
Net cash flows provided by investing activities	(389.8)	128.0
Cash flows from financing activities:
Purchases of treasury stock	(5,029.1)	(3,057.3)
Payments related to issuance of stock for share-based compensation arrangements, net	(19.2)	(23.6)
Proceeds from borrowings	2,967.3	0.0
Repayment of borrowings	(1,500.0)	0.0
Cash proceeds from settlement of swap	3.3	0.0
Net distribution to noncontrolling interest	0.0	4.3
Other	19.0	21.6
Net cash flows used in financing activities	(3,558.7)	(3,055.0)
Net increase (decrease) in cash and cash equivalents	(532.7)	496.5
Effect of exchange rate changes on cash and cash equivalents	(3.9)	(2.3)
Cash and cash equivalents, beginning of the period	2,913.7	1,224.6
Cash and cash equivalents, end of the period	$ 2,384.9	$ 1,723.4

Summary of Significant Accounting Policies (Details)	6 Months Ended
Summary of Significant Accounting Policies (Details)	Jun. 30, 2020 segment
Accounting Policies [Abstract]
Number of reportable segments	1
Interest in subsidiary (less than given percentage)	100.00%

Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2020

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 June 30, 2020		As of December 31, 2019
Commercial paper	$	139.9	$	384.4
Overnight reverse repurchase agreements	247.7		368.8
Money market funds	1,363.7		1,628.5
Short-term debt securities	118.3		159.4
Total	$	1,869.6	$	2,541.1

Marketable debt and equity securities

The following tables summarize our marketable debt and equity securities:



As of June 30, 2020 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,282.5	$	1.5	$	(0.1	)	$	1,283.9
Non-current	502.8		3.8		(0.3		)	506.3
Government securities:
Current	657.7		0.5		—			658.2
Non-current	307.9		0.8		(0.1		)	308.6
Mortgage and other asset backed securities:
Current	0.6		—		—			0.6
Non-current	107.6		0.7		(0.4		)	107.9
Total marketable debt securities	$	2,859.1	$	7.3	$	(0.9	)	$	2,865.5
Marketable equity securities, non-current	$	428.0	$	114.6	$	(15.6	)	$	527.0



As of December 31, 2019 (In millions)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate debt securities:
Current	$	1,057.2	$	1.0	$	—		$	1,058.2
Non-current	633.9		3.0		—			636.9
Government securities:
Current	502.9		0.4		—			503.3
Non-current	510.1		0.8		(0.3		)	510.6
Mortgage and other asset backed securities:
Current	0.7		—		—			0.7
Non-current	260.2		0.8		(0.4		)	260.6
Total marketable debt securities	$	2,965.0	$	6.0	$	(0.7	)	$	2,970.3
Marketable equity securities, non-current	$	218.4	$	132.1	$	(13.0	)	$	337.5

Summary of contractual maturities: available-for-sale securities

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



	As of June 30, 2020				As of December 31, 2019
(In millions)	Estimated Fair Value		Amortized Cost		Estimated Fair Value		Amortized Cost
Due in one year or less	$	1,942.7	$	1,940.8	$	1,562.2	$	1,560.8
Due after one year through five years	862.6		858.5		1,234.5		1,230.4
Due after five years	60.2		59.8		173.6		173.8
Total marketable debt securities	$	2,865.5	$	2,859.1	$	2,970.3	$	2,965.0

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Proceeds from maturities and sales	$	1,490.6		$	1,766.6		$	3,879.9		$	3,255.8
Realized gains	6.1			1.0			11.8			1.6
Realized losses	(5.2		)	(0.3		)	(24.3		)	(0.6		)

Business Acquisition (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 07, 2019
Business Acquisition [Line Items]
Goodwill	$ 5,751.0	$ 5,757.8
Nightstar
Business Acquisition [Line Items]
In-process research and development			$ 700.0

Collaborative and Other Relationships - Equity Method Investments (Details) $ in Millions, ₩ in Billions	1 Months Ended		3 Months Ended					6 Months Ended
	Nov. 30, 2018 USD ($)	Nov. 30, 2018 KRW (₩)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 KRW (₩)	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 KRW (₩)	Nov. 07, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Our share of Samsung Bioepis gains (losses)			$ (15.1)		$ 16.3			$ (0.4)	$ 45.0
Collaboration profit (loss) sharing			21.8		63.5			93.5	121.6
Total revenues			$ 3,681.6		$ 3,616.7			$ 7,215.9	$ 7,106.5
Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Percentage of stake in entity					5.00%				5.00%
Percentage of stake in entity maximum			49.90%					49.90%		49.90%
Payments to acquire additional investment in equity method investment	$ 676.6	₩ 759.5					$ 676.6
Amortization of basis differences														$ 675.0
Loss recorded on Samsung Bioepis joint venture			$ 15.1					$ 0.4
Investment in Samsung Bioepis			557.5					$ 557.5		₩ 668.3		$ 580.2	₩ 670.8
Biogen share of co-promotion profits or losses								50.00%
Collaboration profit (loss) sharing			55.4		$ 63.4			$ 127.2	$ 121.5
Eisai
Schedule of Equity Method Investments [Line Items]
Loss on research and development contracts terminated with Eisai						$ 45.0
Our share of Samsung Bioepis gains (losses)			(33.8)					(33.8)
Additional Milestone Payment			75.0					75.0
Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Upfront and milestone payments made to collaborative partner				$ 100.0
Research and development expense				63.0
Prepaid research and development expenses											$ 37.0
Estimated additional payments upon achievement of development and commercial milestones				210.0
Additional Milestone Payment											$ 15.0
Contract Option Exercise Fee				$ 60.0
Due from Related Parties			13.3					13.3				85.0
Due to Related Parties			0.0					0.0				100.0
Collaborative arrangement \| Samsung Bioepis
Schedule of Equity Method Investments [Line Items]
Total revenues			$ 4.5		$ 52.2			$ 8.2	$ 77.0
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
Neurimmune \| Regulatory Milestones [Member]
Schedule of Equity Method Investments [Line Items]
Potential Future Milestone Payments Commitment To Third Party Approximately												$ 75.0

Financial Instruments Financial Instruments (Details Textual 2) - USD ($) shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Apr. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Proceeds from sales of strategic investments	$ 0.5	$ 309.7
Strategic Investments
Business Acquisition [Line Items]
Strategic investment portfolio	$ 583.2
Other noncurrent assets \| Strategic Investments
Business Acquisition [Line Items]
Strategic investment portfolio				$ 393.9
Sangamo
Business Acquisition [Line Items]
Investment in common stock, shares purchased			24

Share-Based Payments (Tables)

6 Months Ended

Jun. 30, 2020

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Research and development	$	15.2		$	28.1		$	48.5		$	49.8
Selling, general and administrative	30.3			54.8			73.4			82.6
Subtotal	45.5			82.9			121.9			132.4
Capitalized share-based compensation costs	(1.5		)	(2.8		)	(3.0		)	(6.1		)
Share-based compensation expense included in total cost and expenses	44.0			80.1			118.9			126.3
Income tax effect	(7.0		)	(13.6		)	(20.3		)	(21.0		)
Share-based compensation expense included in net income attributable to Biogen Inc.	$	37.0		$	66.5		$	98.6		$	105.3

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 June 30,						For the Six Months Ended June 30,
(In millions)	2020			2019			2020			2019
Market stock units	$	7.4		$	7.8		$	26.5		$	15.5
Time-vested restricted stock units	34.5			31.8			72.0			66.5
Cash settled performance units	(0.1		)	0.4			(1.7		)	(0.6		)
Performance units	—			0.3			(0.1		)	0.8
Performance stock units settled in stock	2.1			12.1			12.4			14.1
Performance stock units settled in cash	(4.0		)	0.9			4.9			1.9
Employee stock purchase plan	5.6			3.4			7.9			8.0
NST stock options	—			26.2			—			26.2
Subtotal	45.5			82.9			121.9			132.4
Capitalized share-based compensation costs	(1.5		)	(2.8		)	(3.0		)	(6.1		)
Share-based compensation expense included in total cost and expenses	$	44.0		$	80.1		$	118.9		$	126.3

Inventory (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Components of inventories
Raw materials	$ 244.7	$ 169.7
Work in process	509.1	460.0
Finished goods	198.9	174.5
Total inventory	$ 952.7	$ 804.2

Financial Instruments (Details 2) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Summary of Contractual Maturities: Available-for-Sale Securities
Due in one year or less, amortized cost	$ 1,942.7	$ 1,562.2
Due in one year or less, estimated fair value	1,940.8	1,560.8
Due after one year through five years, amortized cost	862.6	1,234.5
Due after one year through five years, estimated fair value	858.5	1,230.4
Due after five years, amortized cost	60.2	173.6
Due after five years, estimated fair value	59.8	173.8
Amortized cost	2,859.1	2,965.0
Available-for-sale Securities	$ 2,865.5	$ 2,970.3

Divestitures Divestitures	6 Months Ended
Divestitures Divestitures	Jun. 30, 2020
Divestitures [Abstract]
Divestitures	Divestiture of Hillerød, Denmark Manufacturing Operations In March 2019 we entered into a share purchase agreement with FUJIFILM Corporation (FUJIFILM) to sell all of the outstanding shares of our subsidiary that owned our biologics manufacturing operations in Hillerød, Denmark. We determined that the assets and liabilities related to our Hillerød, Denmark manufacturing operations met the criteria to be classified as held for sale. For the six months ended June 30, 2019, we recorded a loss of approximately $174.5 million in our condensed consolidated statements of income. This estimated loss included a pre-tax loss of $113.2 million, which reflected a $2.3 million decrease to our original estimate as of March 31, 2019, reflecting our estimated fair value of the assets and liabilities held for sale as of June 30, 2019, adjusted for our expected costs to sell our Hillerød, Denmark manufacturing operations of approximately $10.0 million and included our initial estimate of the fair value of an adverse commitment of approximately $120.0 million associated with the guarantee of future minimum batch production at the Hillerød facility. The value of this adverse commitment was determined using a probability-weighted estimate of future manufacturing activity. In addition, we recorded a tax expense of $61.3 million related to the planned transaction during the six months ended June 30, 2019. In August 2019 this transaction closed and we received approximately $881.9 million in cash, which may be adjusted based on the contractual terms discussed below. We determined that the operations disposed of in this transaction did not meet the criteria to be classified as discontinued operations under the applicable guidance. As part of this transaction, we provided FUJIFILM with certain minimum batch production commitment guarantees. There is a risk that the minimum contractual batch production commitments will not be met. Our estimate of the adverse commitment obligation is approximately $74.0 million as of June 30, 2020 and December 31, 2019. We developed this estimate using a probability-weighted estimate of future manufacturing activity and may adjust this estimate based upon changes in business conditions, which may result in the increase or reduction of this adverse commitment obligation in subsequent periods. We also may be obligated to indemnify FUJIFILM for liabilities that existed relating to certain business activities incurred prior to the closing of this transaction. Our estimate of the fair value of the adverse commitment obligation is a Level 3 measurement and is based on forecasted batch production at the Hillerød facility. In addition, we may earn certain contingent payments based on future manufacturing activities at the Hillerød facility. For the disposition of a business, our policy is to recognize contingent consideration when the consideration is realizable. Consistent with our assessment as of the transaction date, we currently believe the probability of earning these payments is remote and therefore we did not include these contingent payments in our calculation of the fair value of the operations. As part of this transaction, we entered into certain manufacturing services agreements with FUJIFILM pursuant to which FUJIFILM will use the Hillerød facility to produce commercial products for us, such as TYSABRI, as well as other third-party products. In addition, we sold to FUJIFILM $41.8 million of raw materials that were remaining at the Hillerød facility on the closing date of this transaction in the third quarter of 2019. These materials were sold at cost, which approximated fair value.

Income Taxes (Tables)

6 Months Ended

Jun. 30, 2020

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 June 30,				For the Six Months Ended June 30,
	2020		2019		2020		2019
Statutory rate	21.0	%	21.0	%	21.0	%	21.0	%
State taxes	0.4		0.9		0.5		0.6
Taxes on foreign earnings	(3.4	)	(4.6	)	(3.7	)	(4.6	)
Tax credits	(1.0	)	(0.9	)	(1.0	)	(0.8	)
Purchased intangible assets	0.2		0.4		0.2		0.4
Divestiture of Denmark manufacturing operations	—		—		—		2.2
Internal reorganization of certain intellectual property rights	—		(5.0	)	—		(2.4	)
TECFIDERA impairment	2.7		—		1.5		—
GILTI	1.5		1.4		1.1		1.7
Other permanent items	0.1		0.4		0.1		0.3
Other	0.4		0.5		0.1		0.1
Effective tax rate	21.9	%	14.1	%	19.8	%	18.5	%

Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Payments for repurchase of common stock		$ 5,029.1	$ 3,057.3
December 2019 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 5,000.0
Repurchase of common stock, at cost, shares	9.0	12.2
Payments for repurchase of common stock	$ 2,800.0	$ 3,700.0
2019 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 5,000.0
Repurchase of common stock, at cost, shares		4.1
Payments for repurchase of common stock		$ 1,300.0
Amount remaining under 2019 Share Repurchase Program	$ 1,300.0	$ 1,300.0

Financial Instruments (Details Textual)	6 Months Ended
Financial Instruments (Details Textual)	Jun. 30, 2020	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Average maturity of marketable securities, months	14 months	14 months

Intangible Assets and Goodwill (Tables)

6 Months Ended

Jun. 30, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets

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



		As of June 30, 2020							As of December 31, 2019
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Completed technology	4-28 years	$	7,379.3	$	(5,014.4	)	$	2,364.9	$	7,379.3	$	(4,881.4	)	$	2,497.9
In-process research and development	Indefinite until commercialization	954.9		—			954.9		965.5		—			965.5
Trademarks and trade names	Indefinite	64.0		—			64.0		64.0		—			64.0
Total intangible assets		$	8,398.2	$	(5,014.4	)	$	3,383.8	$	8,408.8	$	(4,881.4	)	$	3,527.4

Estimated future amortization for acquired intangible assets

he estimated future amortization of acquired intangible assets for the next five years is expected to be as follows:



(In millions)	As of June 30, 2020
2020 (remaining six months)	$	126.0
2021	220.0
2022	220.0
2023	230.0
2024	230.0
2025	220.0

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 June 30, 2020
Goodwill, beginning of period	$	5,757.8
Other	(6.8		)
Goodwill, end of period	$	5,751.0

Inventory

6 Months Ended

Jun. 30, 2020

Inventory Disclosure [Abstract]

Inventory

The components of inventory are summarized as follows:



(In millions)	As of June 30, 2020		As of December 31, 2019
Raw materials	$	244.7	$	169.7
Work in process	509.1		460.0
Finished goods	198.9		174.5
Total inventory	$	952.7	$	804.2

Divestitures (Details Textual) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Divestitures (Details Textual) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Aug. 01, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on divestiture of Hillerød, Denmark manufacturing operations	$ 0.0		$ 0.0	$ 113.2
Inventory raw materials sold to FUJIFILM						$ 41.8
Denmark Manufacturing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration expected to be received for sale of Denmark Manufacturing Operations						$ 881.9
Future minimum batch production for Denmark Manufacturing Operations	$ 74.0	$ 120.0	74.0	120.0
Loss on divestiture of Hillerød, Denmark manufacturing operations, net of tax		2.3		174.5
Loss on divestiture of Hillerød, Denmark manufacturing operations		(2.3)		$ 113.2
Expected costs to sell disposal group		$ 10.0
Tax expense on disposal group			$ 61.3		$ 61.3

- Definition

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

+ References + Details

Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Income Taxes (Details Textual) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Income Tax Contingency [Line Items]
Deferred tax assets, other				$ 856.7
Deferred tax liabilities, other				$ 685.3
Decrease in unrecognized tax benefits is reasonably possible			$ 75.0
Denmark Manufacturing Operations
Income Tax Contingency [Line Items]
Tax expense on disposal group		$ 61.3	$ 61.3
TECFIDERA
Income Tax Contingency [Line Items]
Deferred tax assets, decrease in value	$ 1,324.0	1,324.0
Deferred tax liabilities, decrease in value	1,268.0	1,268.0
Income tax expense associated with reductions in deferred tax assets and liabilities	$ 56.0	$ 56.0

Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income attributable to Biogen Inc.	$ 1,542.1	$ 1,494.1	$ 2,941.2	$ 2,902.9
Weighted-average shares used in calculating:
Weighted average number of common shares outstanding	160.6	190.3	166.7	193.4
Effect of dilutive securities:
Dilutive potential common shares	0.3	0.1	0.3	0.3
Shares used in calculating diluted earnings per share	160.9	190.4	167.0	193.7
Time-vested restricted stock units
Effect of dilutive securities:
Stock units	0.1	0.1	0.1	0.2
Market stock units
Effect of dilutive securities:
Stock units	0.1	0.0	0.1	0.1
Performance stock units settled in stock
Effect of dilutive securities:
Stock units	0.1	0.0	0.1	0.0