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Other Postretirement Employee Benefit Plans (Weighted Average Assumptions Used To Determine Benefit Obligations) (Details) - Other postretirement benefits
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 3.10% 4.20%
Medical trend rate - initial 5.70% 6.00%
Medical trend rate - grading period 18 years 19 years
Medical trend rate - ultimate 4.50% 4.50%