Income Taxes - Income Tax Components (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of income before taxes
United States									$ 21.7	$ 23.5	$ 21.4
Foreign									3.4	2.4	2.2
Earnings before income taxes	$ 3.8	$ 7.9	$ 10.2	$ 3.2	$ 10.3	$ 7.8	$ 10.5	$ (2.7)	25.1	25.9	23.6
Current provision:
U.S. federal									11.5	9.5	3.2
Foreign									1.2	0.8	0.7
State									1.8	1.6	2.2
Total current									14.5	11.9	6.1
Deferred provision:
U.S. federal									(4.9)	(1.5)	2.3
Foreign									0.1	0.1	(0.1)
State									(4.9)	(10.7)	0.5
Total deferred									(9.7)	(12.1)	2.7
Income tax (benefit) expense	$ 0.4	$ 3.5	$ (0.4)	$ 1.3	$ 0.2	$ 2.8	$ 4.2	$ (7.4)	$ 4.8	$ (0.2)	$ 8.8