Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Additional Information (Detail)

v3.20.2
Stock Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Amortization of non-vested stock grants and performance-based awards $ 1,149,000 $ 839,000 $ 2,273,000 $ 2,235,000
Stock options exercised by employees and directors 0 0 0 0
Number of shares of non-vested stock that vested 10,234 6,752 17,397 23,573
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock option plan, share based compensation, vesting period (in years)     3 years  
Aggregate fair value     $ 400,000  
Performance Shares [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares granted under performance plan     7,294  
Employees and Directors [Member] | Non-Vested Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares of non-vested stock issued     16,415  
Aggregate fair value     $ 1,500,000  
Employees and Directors [Member] | Non-Vested Shares [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock option plan, share based compensation, vesting period (in years)     1 year  
Fair market value of the non-vested stock on the date of grant     $ 87.59  
Employees and Directors [Member] | Non-Vested Shares [Member] | Maximum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock option plan, share based compensation, vesting period (in years)     5 years  
Fair market value of the non-vested stock on the date of grant     $ 108.20