Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Stock Based Compensation -Summary of Stock-based Compensation Costs Recognized (Detail) - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total $ 3,171,392 $ 4,609,208
Restricted Stock Units (RSUs) [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 3,083,567 4,251,961
Performance Share Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 0 202,702
Employee Stock Purchase Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense $ 87,825 $ 154,545