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Employee Benefit Plans (Narrative) (Details) - Other Postretirement Benefits
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Minimum    
Defined Benefit Plan Disclosure [Line Items]    
Deferred Compensation Arrangement with Individual, Requisite Age   50 years
Deferred Compensation Arrangement with Individual, Requisite Service Period 10 years  
Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Deferred Compensation Arrangement with Individual, Requisite Age   55 years
Deferred Compensation Arrangement with Individual, Requisite Service Period 20 years