Income Taxes - Summary of Tax Effects of Temporary Differences (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets
Federal foreign tax credit carryforward	$ 37.3	$ 22.0
State net operating loss carryforwards	5.9	5.9
Tax basis goodwill and intangibles	259.8	290.9
Depreciation and amortization	25.4	18.9
Deferred restricted stock unit compensation	24.7	31.4
Lease liabilities	119.0	113.4
Accrued compensation	781.3	883.6
Basis difference in investments	0.0	22.9
Other	140.4	118.2
Deferred tax assets before valuation allowance	1,393.8	1,507.2
Valuation allowance	(56.7)	(46.8)
Total deferred tax assets	1,337.1	1,460.4
Deferred tax liabilities
Unrealized appreciation on investments	1,558.0	1,804.9
Lease right-of-use assets	89.2	85.0
Basis difference in investments	47.9	0.0
Other	28.9	43.1
Total deferred tax liabilities	1,724.0	1,933.0
Net deferred tax assets (liabilities)	(386.9)	(472.6)
Amount of deferred tax liabilities offset for presentation purposes	$ 1,321.3	$ 1,445.9