Marketable Securities - Schedule of Investments in Available For Sale Debt Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 6,600.9	$ 3,649.2
Unrealized Gains	21.0	40.1
Unrealized Losses	(7.0)	(0.2)
Fair Value	6,614.9	3,689.1
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	5,911.8	3,053.0
Unrealized Gains	19.9	37.5
Unrealized Losses	(6.9)	(0.2)
Fair Value	5,924.8	3,090.3
U.S. government and government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	101.2	127.6
Unrealized Gains	0.6	1.3
Unrealized Losses	(0.1)	0.0
Fair Value	101.7	128.9
Sovereign bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	64.6	65.2
Unrealized Gains	0.5	1.1
Unrealized Losses	0.0	0.0
Fair Value	65.1	66.3
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	272.6	276.0
Unrealized Gains	0.0	0.1
Unrealized Losses	0.0	0.0
Fair Value	272.6	276.1
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	231.7	127.4
Unrealized Gains	0.0	0.1
Unrealized Losses	0.0	0.0
Fair Value	231.7	$ 127.5
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	19.0
Unrealized Gains	0.0
Unrealized Losses	0.0
Fair Value	$ 19.0