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Pension and Other Postretirement Employee Benefits (Narrative) (Details) - USD ($)
3 Months Ended 6 Months Ended
Mar. 31, 2020
Jun. 30, 2021
Jun. 30, 2020
Feb. 29, 2020
Defined Benefit Plan Disclosure [Line Items]        
Funding of pension and other postretirement benefit plans   $ 3,833,000 $ 2,839,000  
Pension Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Change in monthly retirement benefit amount   $ 0    
Non-cash pretax settlement charge $ 43,000,000.0      
Qualified Plan [Member] | Pension Plans [Member] | Funded with Plan Assets [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Transfer of outstanding pension benefit obligation related to qualified pension plans to insurance company       $ 101,100,000
Reduction in funded status of qualified pension plans $ 26,200,000