Basic and Diluted (Loss) Earnings Per Common Share - Components of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
(Loss) Income from continuing operations	$ (15.0)	$ 0.1	$ 4.2	$ 16.4
Income from discontinued operations			0.4	0.6
Net income	$ (15.0)	$ 0.1	$ 4.6	$ 17.0
Denominator:
Weighted average common shares outstanding - Basic	52,356,641	52,182,848	52,345,895	52,170,839
Effect of dilutive restricted stock		163,009	11,016	148,815
Weighted average common shares outstanding - Diluted	52,356,641	52,345,857	52,356,911	52,319,654
Basic (loss) earnings per share:
Continuing operations	$ (0.29)		$ 0.08	$ 0.31
Discontinued operations			$ 0.01	$ 0.01
Net (loss) income	$ (0.29)		$ 0.09	$ 0.32
Diluted (loss) earnings per share:
Continuing operations	$ (0.29)		$ 0.08	$ 0.31
Discontinued operations			$ 0.01	$ 0.01
Net (loss) income	$ (0.29)		$ 0.09	$ 0.32