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Pension and Other Postretirement Benefits (Weighted Average Discount Rates used to Calculate the Benefit Obligations (Details) - Other Postretirement Benefits
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligations 3.50% 4.50% 3.80%
Service cost 4.80% 4.90% 5.00%
Interest cost 4.20% 4.10% 3.50%