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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2017
Mar. 31, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2017
Income Taxes [Line Items]            
Income tax expense $ 4,220   $ 4,431 $ 4,132 $ 5,526  
Effective income tax rate       31.20% 38.70%  
Decrease in income tax expense       $ (1,400)    
Benefit from settlement of tax audit   $ (1,300)        
Anticipated [Member]            
Income Taxes [Line Items]            
Effective income tax rate           36.00%