Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale debt securities:
Available-for-sale debt securities	$ 9,750.2	$ 8,397.2
Corporate bonds
Available-for-sale debt securities:
Available-for-sale debt securities	8,216.2	7,487.7
U.S. government and government agency obligations
Available-for-sale debt securities:
Available-for-sale debt securities	381.9	108.5
Sovereign bonds
Available-for-sale debt securities:
Available-for-sale debt securities	53.7	64.4
Commercial paper
Available-for-sale debt securities:
Available-for-sale debt securities	711.4	439.6
Certificates of deposit
Available-for-sale debt securities:
Available-for-sale debt securities	343.3	255.1
Asset-backed securities
Available-for-sale debt securities:
Available-for-sale debt securities	43.7	41.9
Measured on a recurring basis
Available-for-sale debt securities:
Total marketable securities	10,788.9	9,647.1
Measured on a recurring basis | Unrestricted
Available-for-sale debt securities:
Equity securities	43.9	58.4
Measured on a recurring basis | Restricted
Available-for-sale debt securities:
Equity securities	994.8	1,191.5
Measured on a recurring basis | Corporate bonds
Available-for-sale debt securities:
Available-for-sale debt securities	8,216.2	7,487.7
Measured on a recurring basis | U.S. government and government agency obligations
Available-for-sale debt securities:
Available-for-sale debt securities	381.9	108.5
Measured on a recurring basis | Sovereign bonds
Available-for-sale debt securities:
Available-for-sale debt securities	53.7	64.4
Measured on a recurring basis | Commercial paper
Available-for-sale debt securities:
Available-for-sale debt securities	711.4	439.6
Measured on a recurring basis | Certificates of deposit
Available-for-sale debt securities:
Available-for-sale debt securities	343.3	255.1
Measured on a recurring basis | Asset-backed securities
Available-for-sale debt securities:
Available-for-sale debt securities	43.7	41.9
Measured on a recurring basis | Level 1
Available-for-sale debt securities:
Total marketable securities	1,038.7	1,249.9
Measured on a recurring basis | Level 1 | Unrestricted
Available-for-sale debt securities:
Equity securities	43.9	58.4
Measured on a recurring basis | Level 1 | Restricted
Available-for-sale debt securities:
Equity securities	994.8	1,191.5
Measured on a recurring basis | Level 1 | Corporate bonds
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 1 | U.S. government and government agency obligations
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 1 | Sovereign bonds
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 1 | Commercial paper
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 1 | Certificates of deposit
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 1 | Asset-backed securities
Available-for-sale debt securities:
Available-for-sale debt securities	0.0	0.0
Measured on a recurring basis | Level 2
Available-for-sale debt securities:
Total marketable securities	9,750.2	8,397.2
Measured on a recurring basis | Level 2 | Unrestricted
Available-for-sale debt securities:
Equity securities	0.0	0.0
Measured on a recurring basis | Level 2 | Restricted
Available-for-sale debt securities:
Equity securities	0.0	0.0
Measured on a recurring basis | Level 2 | Corporate bonds
Available-for-sale debt securities:
Available-for-sale debt securities	8,216.2	7,487.7
Measured on a recurring basis | Level 2 | U.S. government and government agency obligations
Available-for-sale debt securities:
Available-for-sale debt securities	381.9	108.5
Measured on a recurring basis | Level 2 | Sovereign bonds
Available-for-sale debt securities:
Available-for-sale debt securities	53.7	64.4
Measured on a recurring basis | Level 2 | Commercial paper
Available-for-sale debt securities:
Available-for-sale debt securities	711.4	439.6
Measured on a recurring basis | Level 2 | Certificates of deposit
Available-for-sale debt securities:
Available-for-sale debt securities	343.3	255.1
Measured on a recurring basis | Level 2 | Asset-backed securities
Available-for-sale debt securities:
Available-for-sale debt securities	$ 43.7	$ 41.9