Income Taxes - Tax Rate (Details)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%
State taxes	0.80%	0.70%	0.80%
Taxes on foreign earnings	(10.50%)	(3.30%)	(4.50%)
Tax credits	(3.80%)	(1.20%)	(1.10%)
Purchased intangible assets	(1.60%)	0.70%	0.40%
Divestiture of Denmark manufacturing operations	0.00%	(0.40%)	1.00%
Internal reorganization of certain intellectual property rights	0.00%	0.00%	(2.10%)
TECFIDERA impairment	0.00%	1.80%	0.00%
GILTI	1.30%	1.30%	1.50%
Swiss tax reform	0.00%	0.00%	(0.80%)
Neurimmune tax impacts	(5.30%)	(0.10%)	0.00%
Other	1.10%	(0.80%)	0.10%
Effective tax rate	3.00%	19.70%	16.30%

Effective Income Tax Rate Reconciliation, Change in Foreign Tax Rate, Percent

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Effective Income Tax Rate Reconciliation, Intellectual Property Rights Reorganization

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Effective Tax Rate Reconciliation, GILTI tax

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 740
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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to disposition of asset. Includes, but is not limited to, intra-entity transfer of asset other than inventory.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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