Basic and Diluted Earnings (Loss) Per Common Share - Components of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Income from continuing operations, net of taxes	$ 7.9	$ 14.2	$ 33.1	$ 37.3
(Loss) income from discontinued operations, net of taxes	(1.7)	0.4	(1.8)	0.9
Net income	$ 6.2	$ 14.6	$ 31.3	$ 38.2
Denominator:
Weighted average common shares outstanding - Basic (shares)	52,440,580	52,356,798	52,422,660	52,356,798
Effect of dilutive restricted stock (shares)	163,131	58,165	170,547	33,137
Weighted average common shares outstanding - Diluted (shares)	52,603,711	52,414,963	52,593,207	52,389,935
Basic earnings per common share:
Continuing operations (usd per share)	$ 0.15	$ 0.27	$ 0.63	$ 0.71
Discontinued operations (usd per share)	(0.03)	0.01	(0.03)	0.02
Net income (usd per share)	0.12	0.28	0.60	0.73
Diluted earnings per common share:
Continuing operations (usd per share)	0.15	0.27	0.63	0.71
Discontinued operations (usd per share)	(0.03)	0.01	(0.03)	0.02
Net income (usd per share)	$ 0.12	$ 0.28	$ 0.60	$ 0.73