Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Federal income tax provision at the statutory rate									$ 29.9	$ 29.0	$ 23.2
State income taxes, net of federal benefit									2.9	2.9	2.3
Decrease in unrecognized tax benefits (inclusive of related interest and penalty)									(0.3)	0.0	(0.9)
Effect of foreign operations									(0.7)	(0.1)	(0.3)
Change in valuation allowance									0.0	(0.1)	0.0
Tax credits and other, net									(0.5)	(0.3)	(0.6)
Income tax provision	$ 11.0	$ 6.7	$ 10.1	$ 3.5	$ 10.5	$ 9.1	$ 8.2	$ 3.6	$ 31.3	$ 31.4	$ 23.7
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Federal income tax provision at the statutory rate									35.00%	35.00%	35.00%
State income taxes, net of federal benefit									3.40%	3.50%	3.50%
Decrease in unrecognized tax benefits (inclusive of related interest and penalty)									(0.40%)	0.00%	(1.40%)
Effect of foreign operations									(0.80%)	(0.10%)	(0.50%)
Non-deductible acquisition costs									0.00%	(0.10%)	0.00%
Tax credits and other, net									(0.60%)	(0.40%)	(0.90%)
Effective tax rate									36.60%	37.90%	35.70%
Income tax benefit related to expiration of statute of limitations for uncertain tax positions and adjustment to prior year's estimates									$ 1.5	$ 0.3