Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Statutory federal income tax rate, amount	$ 210.5	$ 199.4	$ 176.5
State taxes, net of federal effect, amount	36.0	35.4	31.1
Equity based compensation, amount	(28.8)	(26.8)	(19.7)
Effect of rates different than statutory, amount	(0.8)	0.8	0.6
Foreign withholding tax, amount	1.0	2.1	2.8
Effect of US Tax Cuts and Jobs Act on Deferred Taxes, amount	(6.8)	0.0	(1.9)
Other, amount	2.7	2.0	8.1
Income tax expense	$ 213.8	$ 212.9	$ 197.5
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory federal income tax rate, percent	21.00%	21.00%	21.00%
State taxes, net of federal effect, percent	3.60%	3.70%	3.70%
Equity based compensation, percent	(2.90%)	(2.80%)	(2.30%)
Effect of rates different than statutory, percent	(0.10%)	0.10%	0.10%
Foreign withholding tax, percent	0.10%	0.20%	0.30%
Effect of TCJA on deferred taxes and repatriation tax, percent	(0.007)	0	(0.002)
Other, percent	0.30%	0.20%	0.90%
Income tax expense, rate	21.30%	22.40%	23.50%