Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Performance Share Units - Additional Information (Detail)

v3.10.0.1
Stock Based Compensation - Performance Share Units - Additional Information (Detail) - USD ($)
12 Months Ended
May 21, 2015
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance based equity plan market capitalization minimum amount       $ 100,000,000
Performance based equity plan market capitalization maximum amount       $ 1,100,000,000
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   0 0 0
Share based compensation arrangement by share based payment award equity instruments other than options grants in period fair value   $ 3,218,000    
Share based compensation arrangement by share based payment award unamortized value   $ 0    
Performance Shares and Inducement Award [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   1,342,061    
Inducement PSU Award [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   63,908    
Performance Share Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share-based compensation expense   $ 819,816 $ 1,661,650  
Performance Based Equity Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance based equity plan market capitalization minimum amount $ 100,000,000      
Performance based equity plan market capitalization maximum amount $ 1,100,000,000      
Percentage of performance share units to be earned on achievement of market capitalization growth 100.00% 100.00%   100.00%
2015 Performance Share Unit Plan [Member] | Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   1,278,153