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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Investments, Owned, Federal Income Tax Note [Line Items]    
Effective income tax rate reconciliation at federal statutory income tax rate 29.50% 37.00%
Income Tax Expense (Benefit) $ 8,434 $ 16,168
U.S. Federal    
Investments, Owned, Federal Income Tax Note [Line Items]    
Effective income tax rate reconciliation at federal statutory income tax rate 35.00%