Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation -Summary of Stock-based Compensation Costs Recognized (Detail)

v3.19.2
Stock Based Compensation -Summary of Stock-based Compensation Costs Recognized (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Total $ 2,797,933 $ 4,342,880 $ 5,969,325 $ 8,952,088
Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 2,675,184 3,884,725 5,758,751 8,136,686
Performance Share Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 0 204,954 0 407,656
Employee Stock Purchase Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense $ 122,749 $ 253,201 $ 210,574 $ 407,746