Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Capitalized research and development expenses	$ 845.3	$ 0.0
Deferred compensation	416.2	406.6
Accrued expenses	235.6	262.1
Fixed assets and intangible assets	227.6	257.5
Deferred revenue	0.0	57.3
Tax attribute carryforwards	41.3	6.1
Other	15.9	10.8
Total deferred tax assets	1,781.9	1,000.4
Deferred tax liabilities:
Unrealized gains on investments	(58.2)	(123.5)
Net deferred tax assets	$ 1,723.7	$ 876.9