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Stock Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of common stock available for future grant 1,031,456  
Shares remaining outstanding 1,612,871  
Employee Stock Option    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected term of stock options 6 years 10 days 6 years 3 days
Unrecognized employee stock based compensation expense $ 7.4  
Unrecognized employee stock based compensation expense, period for recognition 2 years 11 months 4 days