Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Stock Based Compensation -Summary of Stock-based Compensation Costs Recognized (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Total $ 3,852,656 $ 4,568,716 $ 12,804,744 $ 12,472,870
Restricted Stock Units (RSUs) [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 3,578,276 3,843,186 11,714,962 9,865,351
Performance Share Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 207,206 399,867 614,862 1,601,160
Employee Stock Purchase Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 67,174 79,046 474,920 266,398
Deferred Stock Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Allocated share-based compensation expense 0 0 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 $ 246,617 $ 0 $ 738,599