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Pension and Postretirement Health Care Benefits (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Pension Benefits [Abstract]        
annual interest crediting rates   4.72 4.89 2.03
Target Pension Asset Allocations [Abstract]        
transferred   $ 0 $ 0  
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan        
Pension Benefits [Abstract]        
Total benefit obligation   12 11  
Net benefit cost recognized for financial reporting   2 17  
Pension Plan [Member]        
Pension Benefits [Abstract]        
Total benefit obligation   2,943 2,871 $ 3,718
Defined Benefit Plan, Plan Assets, Amount   2,690 [1] 2,685 [1] 3,670
Net benefit cost recognized for financial reporting   $ 74 $ 114 $ 121
Expected average long-term rate of return on assets (as a percent)   6.93% 6.49% 6.49%
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   100.00% 100.00%  
Pension Plan [Member] | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 759 $ 1,111  
Pension Plan [Member] | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   692 689  
Pension Plan [Member] | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   4 3  
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   1,235 882  
Pension Plan [Member] | Cash        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 233 $ 129  
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   2.00% 2.00%  
Pension Plan [Member] | Cash | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 233 $ 129  
Pension Plan [Member] | Cash | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Cash | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Cash | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Commingled Funds        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   1,726 1,817  
Pension Plan [Member] | Commingled Funds | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   491 935  
Pension Plan [Member] | Commingled Funds | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Commingled Funds | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Commingled Funds | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   1,235 882  
Pension Plan [Member] | Debt Securities        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   687 685  
Pension Plan [Member] | Debt Securities | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Debt Securities | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   683 682  
Pension Plan [Member] | Debt Securities | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   4 3  
Pension Plan [Member] | Debt Securities | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Equity Securities        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 35 $ 47  
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   31.00% 33.00%  
Pension Plan [Member] | Equity Securities | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 35 $ 47  
Pension Plan [Member] | Equity Securities | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Equity Securities | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Equity Securities | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Other        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   9 7  
Pension Plan [Member] | Other | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Other | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   9 7  
Pension Plan [Member] | Other | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   0 0  
Pension Plan [Member] | Other | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [1]   $ 0 $ 0  
Pension Plan [Member] | Long-duration fixed income and interest rate swap securities        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   38.00% 38.00%  
Pension Plan [Member] | Alternative investments        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   20.00% 18.00%  
Pension Plan [Member] | Short-to-intermediate fixed income securities        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   9.00% 9.00%  
Other Postretirement Benefits Plan [Member]        
Pension Benefits [Abstract]        
Total benefit obligation   $ 394 $ 405 $ 511
Defined Benefit Plan, Plan Assets, Amount   356 [2] 364 [2] 442
Net benefit cost recognized for financial reporting   $ 6 $ (2) $ (2)
Expected average long-term rate of return on assets (as a percent)   5.00% 4.10% 4.10%
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   100.00% 100.00%  
Other Postretirement Benefits Plan [Member] | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 55 $ 85  
Other Postretirement Benefits Plan [Member] | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   228 215  
Other Postretirement Benefits Plan [Member] | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   1 1  
Other Postretirement Benefits Plan [Member] | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   72 63  
Other Postretirement Benefits Plan [Member] | Cash        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 33 $ 31  
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   1.00% 1.00%  
Other Postretirement Benefits Plan [Member] | Cash | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 33 $ 31  
Other Postretirement Benefits Plan [Member] | Cash | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Cash | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Cash | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Commingled Funds        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   94 117  
Other Postretirement Benefits Plan [Member] | Commingled Funds | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   22 54  
Other Postretirement Benefits Plan [Member] | Commingled Funds | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Commingled Funds | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Commingled Funds | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   72 63  
Other Postretirement Benefits Plan [Member] | Debt Securities        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   188 176  
Other Postretirement Benefits Plan [Member] | Debt Securities | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Debt Securities | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   187 175  
Other Postretirement Benefits Plan [Member] | Debt Securities | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   1 1  
Other Postretirement Benefits Plan [Member] | Debt Securities | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 0 $ 0  
Other Postretirement Benefits Plan [Member] | Equity Securities        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   9.00% 16.00%  
Other Postretirement Benefits Plan [Member] | Other        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 1 $ (1)  
Other Postretirement Benefits Plan [Member] | Other | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Other | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   1 (1)  
Other Postretirement Benefits Plan [Member] | Other | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Other | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 0 $ 0  
Other Postretirement Benefits Plan [Member] | Long-duration fixed income and interest rate swap securities        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   0.00% 0.00%  
Other Postretirement Benefits Plan [Member] | Alternative investments        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   13.00% 12.00%  
Other Postretirement Benefits Plan [Member] | Short-to-intermediate fixed income securities        
Target Pension Asset Allocations [Abstract]        
Target pension asset allocations (as a percent)   77.00% 71.00%  
Other Postretirement Benefits Plan [Member] | Insurance contracts        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 40 $ 41  
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 1        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 2        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   40 41  
Other Postretirement Benefits Plan [Member] | Insurance contracts | Level 3        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   0 0  
Other Postretirement Benefits Plan [Member] | Insurance contracts | Fair Value Measured at Net Asset Value Per Share        
Pension Benefits [Abstract]        
Defined Benefit Plan, Plan Assets, Amount [2]   $ 0 $ 0  
Forecast | Pension Plan [Member]        
Pension Benefits [Abstract]        
Expected average long-term rate of return on assets for next fiscal year (as a percent) 6.93%      
[1] See Note 10 for further information regarding fair value measurement inputs and methods.
[2] See Note 10 for further information on fair value measurement inputs and methods.