Other Consolidated Financial Statement Detail (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Mar. 31, 2022
Other Income (Expense), Net
Gain on sale of equity interest in Samsung Bioepis(1)	$ 0.0	$ 0.0		$ 0.0	$ (1,505.4)
Litigation settlement agreement	0.0	0.0	$ 900.0	0.0	900.0
Interest income	(95.9)	(23.9)		(252.7)	(39.4)
Interest expense	63.8	59.9		175.4	191.8
(Gains) losses on investments, net	317.3	(101.8)		289.6	167.5
Foreign exchange (gains) losses, net	11.4	11.5		30.8	39.0
Other, net	3.4	(1.7)		5.1	25.2
Other (income) expense	300.0	(56.0)		248.2	(221.3)
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net (gains) losses recognized on equity securities	302.0	(109.8)		273.6	158.1
Less: Net (gains) losses realized on equity securities	4.4	(0.5)		5.3	0.0
Net unrealized (gains) losses recognized on equity securities	297.6	(109.3)		268.3	158.1
Accrued Expenses and Other
Reata acquisition-related accrued expense	1,407.0			1,407.0		$ 0.0
Revenue-related reserves for discounts and allowances	1,072.3			1,072.3		1,035.0
Collaboration expense	276.7			276.7		395.6
Royalties and licensing fees	202.8			202.8		209.4
Collaboration expense	298.3			298.3		277.9
Other	712.7			712.7		746.9
Total accrued expense and other	$ 3,838.4			$ 3,838.4		2,521.4
Samsung Bioepis
Other Income (Expense), Net
Equity, ownership interest	49.90%			49.90%			49.90%
Ionis, Sangamo, Denali and Sage
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Net unrealized (gains) losses recognized on equity securities	$ 295.6	$ 112.5		$ 265.0	$ 198.0
Component of accrued expenses and other
Accrued Expenses and Other
Revenue-related reserves for discounts and allowances	$ 940.9			$ 940.9		$ 891.6