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Income Taxes - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
Income tax expense (benefit) $ 0 $ 0  
Unrecognized tax benefits 0 0  
Accrued penalties or interest related to uncertain tax positions $ 0 $ 0  
Federal corporate income tax rate 21.00%   34.00%