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Income Taxes - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Income Tax [Line Items]        
Income tax expense $ 8,722 $ 30,844 $ 19,340 $ 58,776
Effective income tax rate     26.40%