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Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]          
Statutory tax rate 19.40% 30.50% 19.40% 31.70%  
Liability for uncertain tax position $ 0   $ 0   $ 0