Basic and Diluted Earnings (Loss) Per Common Share - Components of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Income from continuing operations, net of taxes	$ 14.4	$ 27.1	$ 23.1	$ 22.6
Income (loss) from discontinued operations, net of taxes	3.7	(2.4)	0.5	(4.8)
Net income	$ 18.1	$ 24.7	$ 23.6	$ 17.8
Denominator:
Weighted average common shares outstanding - Basic (shares)	52,356,798	52,356,798	52,356,798	52,356,798
Effect of dilutive restricted stock (shares)	29,583	0	20,416	0
Weighted average common shares outstanding - Diluted (shares)	52,386,381	52,356,798	52,377,214	52,356,798
Basic earnings (loss) per common share:
Continuing operations (usd per share)	$ 0.27	$ 0.52	$ 0.44	$ 0.43
Discontinued operations (usd per share)	$ 0.07	$ (0.05)	$ 0.01	$ (0.09)
Basic earnings per share (usd per share)	$ 0.34	$ 0.47	$ 0.45	$ 0.34
Diluted earnings (loss) per common share:
Continuing operations (usd per share)	$ 0.27	$ 0.52	$ 0.44	$ 0.43
Discontinued operations (usd per share)	$ 0.07	$ (0.05)	$ 0.01	$ (0.09)
Diluted earnings per share (usd per share)	$ 0.34	$ 0.47	$ 0.45	$ 0.34