Annual report pursuant to Section 13 and 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 ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total $ 15,802,819 $ 9,508,175 $ 5,951,414
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense 13,043,171 5,735,032 4,225,728
Performance Share Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense 1,661,650 2,285,683 489,239
Deferred Stock Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense 1,362 123,644  
Employee Stock Purchase Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense 331,913 318,735 113,217
Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense $ 764,723 $ 1,045,081 1,037,399
IR Consulting Warrant [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Allocated share-based compensation expense     $ 85,831