v3.25.2
Non-Derivative Fair Value Measurements (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Miscellaneous investments $ 55   $ 55   $ 54
Debt Securities, Available-for-sale, Unrealized Gain     1,600   1,400
Debt Securities, Available-for-sale, Unrealized Loss     47   49
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3 0 $ 0 0 $ 0  
Final Contractual Maturity [Abstract]          
Due in 1 Year or Less 14   14    
Due in 1 to 5 Years 327   327    
Due in 5 to 10 Years 258   258    
Due after 10 Years 275   275    
Total 874   874    
Fair Value Measured on a Recurring Basis | Cost          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Total 2,176 [1]   2,176 [1]   2,130 [2]
Fair Value Measured on a Recurring Basis | Cost | Cash equivalents          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Cash equivalents 56 [1]   56 [1]   39 [2]
Fair Value Measured on a Recurring Basis | Cost | Commingled funds          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Commingled funds 703 [1]   703 [1]   703 [2]
Fair Value Measured on a Recurring Basis | Cost | Debt securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt securities 879 [1]   879 [1]   866 [2]
Fair Value Measured on a Recurring Basis | Cost | Equity securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Equity securities 538 [1]   538 [1]   522 [2]
Fair Value Measured on a Recurring Basis | Fair Value          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Total 3,694 [1]   3,694 [1]   3,494 [2]
NAV 1,032 [1]   1,032 [1]   1,025 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Cash equivalents          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Cash equivalents 56 [1]   56 [1]   39 [2]
NAV 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Commingled funds          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Commingled funds 1,032 [1]   1,032 [1]   1,025 [2]
NAV 1,032 [1]   1,032 [1]   1,025 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Debt securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt securities 874 [1]   874 [1]   846 [2]
NAV 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Equity securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Equity securities 1,732 [1]   1,732 [1]   1,584 [2]
NAV 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Total 1,786 [1]   1,786 [1]   1,622 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Cash equivalents          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Cash equivalents 56 [1]   56 [1]   39 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Commingled funds          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Commingled funds 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Debt securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt securities 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Equity securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Equity securities 1,730 [1]   1,730 [1]   1,583 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Total 866 [1]   866 [1]   833 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Cash equivalents          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Cash equivalents 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Commingled funds          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Commingled funds 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Debt securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt securities 864 [1]   864 [1]   832 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Equity securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Equity securities 2 [1]   2 [1]   1 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Total 10 [1]   10 [1]   14 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Cash equivalents          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Cash equivalents 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Commingled funds          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Commingled funds 0 [1]   0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Debt securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt securities 10 [1]   10 [1]   14 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Equity securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Equity securities $ 0 [1]   $ 0 [1]   $ 0 [2]
[1] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $55 million of other investments, including the rabbi trust.
[2] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $54 million of other investments, including the rabbi trust.