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Stock-Based Compensation (Summary Of Nonvested Share Activity) (Details) - $ / shares
3 Months Ended 9 Months Ended
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Granted, Number of Share Units 5,337 4,874 192,407 6,088 4,594 223,495    
Stock Awards [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Nonvested share units at beginning of period, Number of Share Units            
Granted, Number of Share Units             11,487  
Stock units vested and issued, Number of Share Units             (11,487)  
Nonvested share units at end of period, Number of Share Units            
Nonvested share units at beginning of period, Weighted Average Fair Value            
Granted, Weighted Average Fair Value             45.71 $ 40.54
Share units vested, Weighted Average Fair Value             45.71  
Nonvested share units at end of period, Weighted Average Fair Value