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Share-Based Compensation - Additional Information (Detail)
3 Months Ended 9 Months Ended
Sep. 30, 2021
USD ($)
shares
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
Deferral
shares
Sep. 30, 2020
USD ($)
shares
Dec. 31, 2020
shares
May 10, 2016
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Deferred shares and held by the rabbi trust 243,138   243,138   265,508  
Restricted Stock Units (RSUs) [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards 800,000   800,000      
Long Term Incentive Stock Option [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards 100,000   100,000      
Time-Based RSUs [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Compensation expenses | $ $ 100,000 $ 100,000 $ 400,000 $ 300,000    
Compensation cost expected to be recognized over period | $ 900,000   $ 900,000      
Weighted-average period     2 years      
Performance-Based RSUs [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Weighted-average period     1 year 9 months 18 days      
Performance-based compensation expense (income) | $ 1,200,000 1,200,000 $ 2,600,000 $ 2,600,000    
Remaining compensation expense | $ $ 4,700,000   $ 4,700,000      
Long Term Incentive Plan [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards 900,000   900,000      
2016 Incentive Plan [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards           1,000,000
Incentive plan expiry date     May 10, 2026      
2016 Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards           900,000
2016 Incentive Plan [Member] | Stock Options [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common shares reserved for awards           100,000
Long Term Incentive Plan and 2016 Incentive Plan [Member] | Minimum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Option issued under plan vest and expire     5 years      
Long Term Incentive Plan and 2016 Incentive Plan [Member] | Maximum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Option issued under plan vest and expire     10 years      
Long Term Incentive Plan and 2016 Incentive Plan [Member] | After One Year [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option awards vesting percentage     50.00%      
Long Term Incentive Plan and 2016 Incentive Plan [Member] | After Two Years [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option awards vesting percentage     75.00%      
Long Term Incentive Plan and 2016 Incentive Plan [Member] | After Three Years [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock option awards vesting percentage     100.00%      
Long Term Incentive Plan Stock Option [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Granted, Number of Shares     3,000 25,500    
Exercised, Number of Shares     7,000 3,750    
Long Term Incentive Plan Stock Option [Member] | Maximum [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Compensation expenses | $ $ 100,000 $ 100,000 $ 100,000 $ 100,000    
Weighted-average period     1 year 9 months 18 days      
Expected compensation cost related to unvested awards not yet recognized | $ $ 300,000   $ 300,000      
Deferred Compensation Plan [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of deferrals | Deferral     2