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Income Taxes - Additional Information (Detail)	3 Months Ended
Income Taxes - Additional Information (Detail)	Mar. 31, 2012	Mar. 31, 2011
Income Taxes [Line Items]
Effective tax rate	31.70%	32.50%

- Definition

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.

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