Income Taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Deferred compensation	$ 519.7	$ 458.2
Fixed assets and intangible assets	192.0	107.8
Accrued expenses	75.9	53.3
Deferred revenue	22.0	20.2
Other	0.0	33.3
Total deferred tax assets	809.6	672.8
Valuation allowance	(7.0)	0.0
Deferred tax assets, net of valuation allowance	802.6	672.8
Deferred tax liabilities:
Other	(11.2)	(2.7)
Net deferred tax assets	$ 791.4	$ 670.1