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Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Federal corporate tax rate   21.00% 35.00%
Effective tax rate 24.00% 24.60%  
Adjustment to provisional tax     $ 0