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Other Postretirement Benefit Plans - Assumptions (Details) - Other Postretirement Benefits Plan
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Assumptions:        
Discount rate 3.43%   3.57%  
Rate of return 3.00% 4.85% 4.50%  
Discount rate 2.62% 3.43% 4.30% 3.57%
Minimum        
Assumptions:        
Discount rate   3.48%    
Maximum        
Assumptions:        
Discount rate   4.30%