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Income Taxes - Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%
State taxes	0.70%	0.80%	0.60%
Taxes on foreign earnings	(3.30%)	(4.50%)	(1.90%)
Credits and net operating loss utilization	(1.20%)	(1.10%)	(0.90%)
Purchased intangible assets	0.70%	0.40%	1.20%
Divestiture of Denmark manufacturing operations	(0.40%)	1.00%	0.00%
Internal reorganization of certain intellectual property rights	0.00%	(2.10%)	0.00%
TECFIDERA impairment	1.80%	0.00%	0.00%
GILTI	1.30%	1.50%	1.60%
U.S. tax reform	0.00%	0.00%	2.10%
Swiss tax reform	0.00%	(0.80%)	0.00%
Other	(0.90%)	0.10%	0.50%
Effective tax rate	19.70%	16.30%	24.20%

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