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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Jan. 31, 2017
Jan. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Percentage increase in number of common stock outstanding   5.00%    
Performance Stock Options (PSOs)        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of shares outstanding unvested 90,378      
Unamortized share based compensation expected to be recognized over the remaining vesting period $ 0.3      
Unamortized share based compensation expected recognition period 4 months 28 days      
Performance Stock Units (PSUs) | Maximum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares available for issuance     143,750 102,906
Inducement Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares available for issuance 1,500,000      
2013 Equity Incentive Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock reserved, shares 15,032,633      
2017 Equity Incentive Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock reserved, shares 1,500,000