Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Income Taxes [Line Items]    
Gross unrecognized tax benefit balance, change within the next twelve months, lower limit   $ 0
Gross unrecognized tax benefit balance, change within the next twelve months, upper limit   $ 9.4
Effective income tax rate 36.00% 36.70%