Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Summary of Stock-based Compensation Reflected within Statements of Operations (Detail)

v3.19.3
Stock Based Compensation - Summary of Stock-based Compensation Reflected within Statements of Operations (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Share-based Compensation, Total $ 2,099,675 $ 3,852,656 $ 8,069,000 $ 12,804,744
Research and Development Expense [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 1,154,680 2,051,986 4,172,458 7,594,209
Selling and Marketing Expense [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 390,192 352,941 1,111,185 1,022,832
General and Administrative Expense [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense $ 554,803 $ 1,447,729 $ 2,785,357 $ 4,187,703