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Income Taxes - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]      
Statutory tax rate 35.00% 35.00% 35.00%
Valuation allowance $ 0 $ 0  
State net operating losses 0 0 $ 0
Liability for uncertain tax position $ 0 $ 0