Marketable Securities - Schedule of Fair Value and Unrealized Losses of Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value
Less than 12 Months	$ 12,339.2	$ 7,854.9
12 Months or Greater	1,667.5	4,157.5
Total	14,006.7	12,012.4
Unrealized Losses
Less than 12 Months	(0.8)	(9.0)
12 Months or Greater	(25.2)	(106.8)
Total	(26.0)	(115.8)
Corporate bonds
Fair Value
Less than 12 Months	6,351.7	2,363.3
12 Months or Greater	1,415.6	4,034.7
Total	7,767.3	6,398.0
Unrealized Losses
Less than 12 Months	(0.7)	(2.4)
12 Months or Greater	(23.7)	(102.5)
Total	(24.4)	(104.9)
U.S. government and government agency obligations
Fair Value
Less than 12 Months	5,799.9	4,780.6
12 Months or Greater	198.7	52.7
Total	5,998.6	4,833.3
Unrealized Losses
Less than 12 Months	(0.1)	(6.0)
12 Months or Greater	(1.2)	(2.6)
Total	(1.3)	(8.6)
Sovereign bonds
Fair Value
Less than 12 Months	46.0	12.4
12 Months or Greater	20.9	44.8
Total	66.9	57.2
Unrealized Losses
Less than 12 Months	0.0	(0.1)
12 Months or Greater	(0.2)	(0.8)
Total	(0.2)	(0.9)
Commercial paper
Fair Value
Less than 12 Months		636.8
12 Months or Greater		0.0
Total		636.8
Unrealized Losses
Less than 12 Months		(0.2)
12 Months or Greater		0.0
Total		(0.2)
Asset-backed securities
Fair Value
Less than 12 Months	141.6	61.8
12 Months or Greater	32.3	25.3
Total	173.9	87.1
Unrealized Losses
Less than 12 Months	0.0	(0.3)
12 Months or Greater	(0.1)	(0.9)
Total	$ (0.1)	$ (1.2)