v3.26.1
Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Assets:    
Sub-total $ 50 $ 9
Liabilities:    
Total liabilities 50 9
Equity securities    
Assets:    
Assets measured at net asset value 529 806
Debt securities    
Assets:    
Assets measured at net asset value $ 357 $ 329
Liabilities:    
Debt, weighted average interest rate 4.04% 4.02%
Decommissioning fund investments, debt securities average maturities 8 years 8 years
Decommissioning fund investments, debt maturities, one through five years, fair value $ 958  
Decommissioning fund investments, debt maturities, five through ten years, fair value 1,225  
Decommissioning fund investments, debt maturities, after ten years, fair value 583  
NDTs - other investments    
Assets:    
Assets measured at net asset value 93 $ 28
Commodity Contracts    
Assets:    
Derivative asset 50 8
Liabilities:    
Derivative liabilities 50 8
Interest Rate Swaps    
Assets:    
Derivative asset 0 1
Liabilities:    
Derivative liabilities 0 1
Total    
Assets:    
Sub-total 8,264 7,047
Total assets 9,243 8,210
Liabilities:    
Total liabilities 6,351 5,778
Total | Equity securities    
Assets:    
NDTs 1,858 1,761
Total | Debt securities    
Assets:    
NDTs 2,409 2,088
Total | Commodity Contracts    
Assets:    
Derivative asset 3,994 3,180
Liabilities:    
Derivative liabilities 6,351 5,756
Total | Interest Rate Swaps    
Assets:    
Derivative asset 3 18
Liabilities:    
Derivative liabilities 0 22
Level 1    
Assets:    
Sub-total 5,126 4,040
Liabilities:    
Total liabilities 4,077 3,060
Level 1 | Equity securities    
Assets:    
NDTs 1,858 1,761
Level 1 | Debt securities    
Assets:    
NDTs 164 117
Level 1 | Commodity Contracts    
Assets:    
Derivative asset 3,104 2,162
Liabilities:    
Derivative liabilities 4,077 3,060
Level 1 | Interest Rate Swaps    
Assets:    
Derivative asset 0 0
Liabilities:    
Derivative liabilities 0 0
Level 2    
Assets:    
Sub-total 2,722 2,425
Liabilities:    
Total liabilities 635 867
Level 2 | Equity securities    
Assets:    
NDTs 0 0
Level 2 | Debt securities    
Assets:    
NDTs 2,245 1,971
Level 2 | Commodity Contracts    
Assets:    
Derivative asset 474 437
Liabilities:    
Derivative liabilities 635 846
Level 2 | Interest Rate Swaps    
Assets:    
Derivative asset 3 17
Liabilities:    
Derivative liabilities 0 21
Level 3    
Assets:    
Derivative asset 366 573
Sub-total 366 573
Liabilities:    
Derivative liabilities 1,589 1,842
Total liabilities 1,589 1,842
Level 3 | Equity securities    
Assets:    
NDTs 0 0
Level 3 | Debt securities    
Assets:    
NDTs 0 0
Level 3 | Commodity Contracts    
Assets:    
Derivative asset 366 573
Liabilities:    
Derivative liabilities 1,589 1,842
Level 3 | Interest Rate Swaps    
Assets:    
Derivative asset 0 0
Liabilities:    
Derivative liabilities $ 0 $ 0