Annual report pursuant to Section 13 and 15(d)

Retirement and Long-Term Incentive Plans - Additional Information (Details)

v3.21.1
Retirement and Long-Term Incentive Plans - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Employer discretionary contribution $ 700,000 $ 800,000  
Available shares for future issuance (in shares) 1,611,928    
Share-based compensation cost charged against income $ 1,126,000 $ 1,774,000 $ 2,795,000
Total unrecognized compensation costs $ 1,900,000    
Recognition of compensation cost, weighted average period 1 year 10 months 24 days    
Value of awards granted $ 1,800,000    
Total fair value of shares vested $ 400,000    
Outstanding stock option awards 0    
Stock option awards granted 0 0 0
Performance based share compensation expense   $ 0  
Non-employee directors      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock vesting period 6 months    
Employee Stock Option | Long Term Incentive Plan 1997      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 1,000,000    
Employee Stock Option | Long Term Incentive Plan 2002      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 500,000    
Employee Stock Option | Long Term Incentive Plan 2011      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 500,000    
Employee Stock Option | Long Term Incentive Plan 2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 2,500,000    
Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock vesting period 3 years    
Performance Shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance period awards are earned 3 years    
Performance based share compensation benefit due to reversal of previously recognized expense   $ 1,700,000  
Performance based share compensation expense $ 0   $ 1,100,000
Cash-Based Performance Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance based share compensation expense $ 0    
Performance period awards are earned 3 years    
Target amounts payable associated with performance period $ 500,000