Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Other Income (Expense), Net
Interest income	$ (17.4)	$ (80.9)
Interest expense	69.2	62.5
(Gains) losses on investments, net	30.6	77.7
Foreign exchange (gains) losses, net	9.4	10.7
Other, net	1.9	(0.6)
Other (income) expense	93.7	69.4
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net (gains) losses recognized on equity securities	30.6	78.1
Less: Net (gains) losses realized on equity securities	4.9	1.6
Net unrealized (gains) losses recognized on equity securities	25.7	76.5
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	1,096.7		$ 1,062.0
Employee compensation and benefits	164.1		335.1
Collaboration expense	278.0		214.6
Royalties and licensing fees	161.5		191.5
Reata acquisition-related accrued expense	79.2		117.5
Other	714.8		838.4
Total accrued expense and other	2,354.6		2,623.6
Ionis, Sangamo, Denali and Sage
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net unrealized (gains) losses recognized on equity securities	27.7	$ 100.0
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 957.0		$ 926.5