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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 Taxes [Line Items]        
Provision (benefit) for income taxes $ (145) $ 74 $ 155 $ (5,118)
Effective income tax rate 0.31% 25.70% 0.21% 24.50%
Discrete tax benefits | Reduction of Uncertain Tax Positions
       
Income Taxes [Line Items]        
Provision (benefit) for income taxes     100  
Discrete tax benefits | State tax apportionment changes and an adjustment
       
Income Taxes [Line Items]        
Provision (benefit) for income taxes       $ 400