Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Employee Stock Purchase Plan - Additional Information (Detail)

v3.19.1
Stock Based Compensation - Employee Stock Purchase Plan - Additional Information (Detail) - Employee Stock Purchase Plan [Member] - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period, weighted average grant date fair value $ 2.43 $ 13.84
Percentage of proportionate value of call option of stock 85.00%  
Percentage of proportionate value of put option of stock 15.00%  
Allocated share-based compensation expense $ 87,825 $ 154,545