Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Income Taxes [Line Items]
Effective income tax rate	32.00%	33.70%	31.00%	34.00%
Liability for income taxes	$ 10.7		$ 10.7		$ 11.3
Unrecognized tax benefits if recognized that would affect effective tax rate	3.8		3.8		3.7
Accrued interest	2.3		2.3		2.5
Accrued penalties	1.3		1.3		1.4
Unrecognized tax benefits	$ 1.6		$ 1.6

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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The amount of estimated interest accrued as of the balance sheet date arising from income tax examinations.

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The estimated loss resulting from the income tax examination that has been accrued as of the balance sheet date, including interest and penalties.

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The amount of estimated penalties accrued as of the balance sheet date arising from income tax examinations.

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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-Glossary Unrecognized Tax Benefit

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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