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Retirement and Share-based Compensation Plans (Incentive Plans) (Details) - shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
2016 Employee Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized 2,500,000    
Number of shares available for future grant 1,712,924    
2016 Employee Incentive Plan | Performance Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Duration used to measure performance and threshold goals 3 years    
2016 Employee Incentive Plan | Performance Units | 2019 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Equity instruments granted 152,678    
2016 Employee Incentive Plan | Performance Units | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Equity instruments granted   105,617  
2016 Employee Incentive Plan | Performance Units | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Equity instruments granted     84,476
2016 Employee Incentive Plan | Performance Units | Threshold Goals, Vesting Percentage | 2019 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 50.00%    
2016 Employee Incentive Plan | Performance Units | Threshold Goals, Vesting Percentage | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage   50.00%  
2016 Employee Incentive Plan | Performance Units | Threshold Goals, Vesting Percentage | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage     50.00%
2016 Employee Incentive Plan | Performance Units | Target Performance Goals, Vesting Percentage | 2019 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 100.00%    
2016 Employee Incentive Plan | Performance Units | Target Performance Goals, Vesting Percentage | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage   100.00%  
2016 Employee Incentive Plan | Performance Units | Target Performance Goals, Vesting Percentage | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage     100.00%
2016 Employee Incentive Plan | Performance Units | Maximum Performance Goals, Vesting Percentage | 2019 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 150.00%    
2016 Employee Incentive Plan | Performance Units | Maximum Performance Goals, Vesting Percentage | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage   150.00%  
2016 Employee Incentive Plan | Performance Units | Maximum Performance Goals, Vesting Percentage | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage     150.00%
2016 Employee Incentive Plan | Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
2016 Employee Incentive Plan | Restricted Stock Units | 2019 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Equity instruments granted 72,696    
2016 Employee Incentive Plan | Restricted Stock Units | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period   1 year  
Equity instruments granted   85,500  
2016 Employee Incentive Plan | Restricted Stock Units | Share-based Compensation Award, Tranche One | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period   3 years  
Equity instruments granted   6,000  
2016 Employee Incentive Plan | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Participant age for full vesting 65 years    
Requisite service period for full vesting 10 years    
2016 Employee Incentive Plan | Restricted Stock | 2018 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares issued in period   36,270  
2016 Employee Incentive Plan | Restricted Stock | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares issued in period     39,826
2016 Employee Incentive Plan | Restricted Stock | Share-based Compensation Award, Tranche One | 2017 Employee Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period     1 year
Shares issued in period     6,727
2009 Employee Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized 2,500,000    
Duration of award 10 years    
Award vesting period 3 years    
2009 Employee Incentive Plan | March 2010 Option Grant      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Duration of award 6 years    
2013 Director Equity And Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized 250,000    
Number of shares available for future grant 22,900    
2013 Director Equity And Incentive Plan | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares issued in period 32,000 28,600 33,000
Maximum | 2013 Director Equity And Incentive Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 1 year