Reconciliation of Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax provision at statutory rate	$ 115.5	$ 128.7	$ 111.2
Impact of goodwill impairment	21.4	0.0	0.0
Other non-deductible expenses, net	8.2	10.3	4.9
State income taxes, net of federal benefit	24.3	25.7	22.8
Income tax provision, excluding other reconciling items	169.4	164.7	138.9
Change in tax rate	0.0	0.0	(5.0)
Change in valuation allowance, net	0.3	0.2	3.5
Adjustments and settlements	0.7	0.4	(0.7)
Federal and state tax credits	(0.7)	(0.9)	(1.0)
Other, net	(1.4)	(2.6)	(2.2)
Income tax provision	$ 168.3	$ 161.8	$ 133.5
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income tax provision at statutory rate, %	21.00%	21.00%	21.00%	35.00%
Impact of goodwill impairment, %	3.90%	0.00%	0.00%
Other non-deductible expenses, net, %	1.50%	1.70%	0.90%
State income taxes, net of federal benefit, %	4.40%	4.20%	4.30%
Income tax provision, excluding other reconciling items, %	30.80%	26.90%	26.20%
Change in tax rate, %	0.00%	0.00%	(0.90%)
Change in valuation allowance, net, %	0.10%	0.00%	0.70%
Adjustments and settlements, %	0.10%	0.10%	(0.10%)
Federal and state tax credits, %	(0.10%)	(0.20%)	(0.20%)
Other, net, %	(0.30%)	(0.40%)	(0.50%)
Income tax provision, %	30.60%	26.40%	25.20%

The portion of the effective income tax rate that can be explained by: 1) the amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations; 2) nondeductible expenses under enacted tax laws, or differences in the methodologies used to determine expense amounts for financial statements prepared in accordance with generally accepted accounting principles and enacted tax laws; and 3) state and local income tax expense or benefit.

No definition available.