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
Mar. 31, 2015	Mar. 31, 2014
Numerator:
(Loss) income from continuing operations, net of taxes	$ (0.8)	$ 8.7
Loss from discontinued operations, net of taxes	(0.1)	(3.2)
Net (loss) income	$ (0.9)us-gaap_NetIncomeLoss	$ 5.5us-gaap_NetIncomeLoss
Denominator:
Weighted average common shares outstanding - Basic (shares)	52,386,223	52,356,798
Effect of dilutive restricted stock (shares)	0	11,146
Weighted average common shares outstanding - Diluted (shares)	52,386,223	52,367,944
Basic (loss) earnings per common share:
Continuing operations (usd per share)	$ (0.02)	$ 0.17
Discontinued operations (usd per share)	$ 0.00	$ (0.06)
Basic earnings per share (usd per share)	$ (0.02)us-gaap_EarningsPerShareBasic	$ 0.11us-gaap_EarningsPerShareBasic
Diluted (loss) earnings per common share:
Continuing operations (usd per share)	$ (0.02)	$ 0.17
Discontinued operations (usd per share)	$ 0.00	$ (0.06)
Diluted earnings per share (usd per share)	$ (0.02)us-gaap_EarningsPerShareDiluted	$ 0.11us-gaap_EarningsPerShareDiluted

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of income (loss) from a disposal group, net of income tax, reported as a separate component of income before extraordinary items after deduction or consideration of the amount allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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Per diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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