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Employee Benefits - Assumptions (Details)
12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Pension Plan | Benefit obligation assumptions        
Weighted average assumptions - benefit obligations        
Discount rate   5.19% 5.49% 2.96%
Rate of compensation increase   4.00% 4.00%  
Interest credit rate   4.84% 4.61%  
Pension Plan | Net periodic benefit cost assumptions        
Weighted average assumptions - net periodic benefit cost        
Discount rate   5.49% 3.18% 2.71%
Expected return on plan assets   6.62% 6.88% 6.88%
Rate of compensation increase   4.00% 4.00% 4.00%
Interest credit rate   4.62% 3.78% 3.71%
Pension Plan | Net periodic benefit cost assumptions | Subsequent event        
Weighted average assumptions - net periodic benefit cost        
Expected return on plan assets 6.62%      
OPEB Plan | Benefit obligation assumptions        
Weighted average assumptions - benefit obligations        
Discount rate   5.16% 5.50% 2.92%
OPEB Plan | Benefit obligation assumptions | Pre 65        
Medical cost trend rates        
Assumed medical cost trend rate   6.25% 6.50%  
Ultimate trend rate   5.00% 5.00%  
Year ultimate trend rate is reached   2031 2031  
OPEB Plan | Benefit obligation assumptions | Post 65        
Medical cost trend rates        
Assumed medical cost trend rate   6.39% 6.00%  
Ultimate trend rate   5.00% 5.00%  
Year ultimate trend rate is reached   2030 2031  
OPEB Plan | Net periodic benefit cost assumptions        
Weighted average assumptions - net periodic benefit cost        
Discount rate   5.50% 2.92% 2.66%
Expected return on plan assets   6.50% 7.00% 7.00%
OPEB Plan | Net periodic benefit cost assumptions | Subsequent event        
Weighted average assumptions - net periodic benefit cost        
Expected return on plan assets 6.50%      
OPEB Plan | Net periodic benefit cost assumptions | Pre 65        
Medical cost trend rates        
Assumed medical cost trend rate   6.50% 5.70% 5.85%
Ultimate trend rate   5.00% 5.00% 5.00%
Year ultimate trend rate is reached   2031 2028 2028
OPEB Plan | Net periodic benefit cost assumptions | Post 65        
Medical cost trend rates        
Assumed medical cost trend rate   6.00% 5.67% 5.80%
Ultimate trend rate   5.00% 5.00% 5.00%
Year ultimate trend rate is reached   2031 2028 2028