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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Income Tax Disclosure [Abstract]      
Income tax expense or benefit $ 0 $ 0  
Federal corporate income tax rate 21.00%   34.00%
Tax cuts and jobs act of 2017, deduction for net operating losses percentage of taxable income     80.00%