Other Consolidated Financial Statement Detail - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Unrealized gains (losses) recognized during the period on equity securities		$ (831,400,000)	$ 681,800,000	$ 150,100,000
Other long-term liabilities		1,320,500,000	1,329,600,000
Accrued income taxes		664,500,000	$ 709,900,000
Denali, Ionis, Sage, and Sangamo
Business Acquisition [Line Items]
Unrealized gains (losses) recognized during the period on equity securities		(819,600,000)
Fumarate | Fumapharm AG | Twenty billion
Business Acquisition [Line Items]
Increase to goodwill	$ 300,000,000
Cumulative sales level				$ 20,000,000,000
Fumarate | Fumapharm AG | Each additional one billion up to twenty billion
Business Acquisition [Line Items]
Cumulative sales level	$ 20,000,000,000	$ 20,000,000,000