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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Income Tax Disclosure [Line Items]        
Deferred tax assets, valuation allowance $ 39,806 $ 39,806   $ 24,888
Effective tax rate   1.00% 0.00%  
Change in valuation allowance   $ 14,918    
ASU No. 2016-09 [Member]        
Income Tax Disclosure [Line Items]        
Unrecognized excess tax benefits of deferred tax assets offset by valuation allowance       $ 6,219
Excess tax benefits recognized in the provision for income taxes offset by valuation allowance $ 296 $ 1,397