Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Stock Based Compensation -Summary of Stock-based Compensation Costs Recognized (Detail) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total $ 4,609,208 $ 3,538,191
Restricted Stock Units (RSUs) [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 4,251,961 2,602,775
Performance Share Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 202,702 613,860
Employee Stock Purchase Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 154,545 93,811
Deferred Stock Units [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense 0 1,362
Employee Stock Option [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Allocated share-based compensation expense $ 0 $ 226,383