Fair Value Measurements - Financial Assets and Liabilities Subject to Fair Value Measurements (Details) - Recurring Basis - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financial instruments carried at fair value (asset positions):
Cash equivalents	$ 5,865.3	$ 7,033.9
Prepaid expenses and other current assets, foreign currency forward contracts	26.3	1.8
Total financial assets	11,286.3	10,382.7
Financial instruments carried at fair value (liability positions):
Other current liabilities, foreign currency forward contracts	(1.4)	(33.7)
Contingent consideration	(77.3)	(77.4)
Total financial liabilities	(78.7)	(111.1)
Level 1
Financial instruments carried at fair value (asset positions):
Cash equivalents	4,921.3	5,397.3
Prepaid expenses and other current assets, foreign currency forward contracts	0.0	0.0
Total financial assets	6,354.1	5,989.8
Financial instruments carried at fair value (liability positions):
Other current liabilities, foreign currency forward contracts	0.0	0.0
Contingent consideration	0.0	0.0
Total financial liabilities	0.0	0.0
Level 2
Financial instruments carried at fair value (asset positions):
Cash equivalents	944.0	1,636.6
Prepaid expenses and other current assets, foreign currency forward contracts	26.3	1.8
Total financial assets	4,932.2	4,392.9
Financial instruments carried at fair value (liability positions):
Other current liabilities, foreign currency forward contracts	(1.4)	(33.7)
Contingent consideration	0.0	0.0
Total financial liabilities	(1.4)	(33.7)
Level 3
Financial instruments carried at fair value (asset positions):
Cash equivalents	0.0	0.0
Prepaid expenses and other current assets, foreign currency forward contracts	0.0	0.0
Total financial assets	0.0	0.0
Financial instruments carried at fair value (liability positions):
Other current liabilities, foreign currency forward contracts	0.0	0.0
Contingent consideration	(77.3)	(77.4)
Total financial liabilities	(77.3)	(77.4)
Corporate equity securities
Financial instruments carried at fair value (asset positions):
Marketable securities:	43.4	46.0
Corporate equity securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	43.4	46.0
Corporate equity securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Corporate equity securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
U.S. Treasury securities
Financial instruments carried at fair value (asset positions):
Marketable securities:	1,389.4	546.5
U.S. Treasury securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	1,389.4	546.5
U.S. Treasury securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
U.S. Treasury securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
U.S. government agency securities
Financial instruments carried at fair value (asset positions):
Marketable securities:	356.7	425.2
U.S. government agency securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
U.S. government agency securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	356.7	425.2
U.S. government agency securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Asset-backed securities
Financial instruments carried at fair value (asset positions):
Marketable securities:	792.6	306.0
Asset-backed securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Asset-backed securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	792.6	306.0
Asset-backed securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Certificates of deposit
Financial instruments carried at fair value (asset positions):
Marketable securities:	42.6	33.7
Certificates of deposit \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Certificates of deposit \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	42.6	33.7
Certificates of deposit \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Corporate debt securities
Financial instruments carried at fair value (asset positions):
Marketable securities:	2,632.2	1,802.8
Corporate debt securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Corporate debt securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	2,632.2	1,802.8
Corporate debt securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Commercial paper
Financial instruments carried at fair value (asset positions):
Marketable securities:	137.8	186.8
Commercial paper \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities:	0.0	0.0
Commercial paper \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities:	137.8	186.8
Commercial paper \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities:	$ 0.0	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in marketable security.

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