Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Deferred compensation	$ 406.6	$ 436.6
Accrued expenses	262.1	139.8
Fixed assets and intangible assets	257.5	140.5
Deferred revenue	57.3	44.6
Other	16.9	14.9
Total deferred tax assets	1,000.4	776.4
Deferred tax liabilities:
Unrealized gains on investments	(123.5)	(57.7)
Net deferred tax assets	$ 876.9	$ 718.7