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Non-Derivative Fair Value Measurements (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 31, 2024
Nuclear decommissinoning fund [Abstract]      
Equity investments in unconsolidated subsidiaries $ 241   $ 246
Miscellaneous investments 156   156
Debt Securities, Available-for-sale, Unrealized Gain 1,400    
Debt Securities, Available-for-sale, Unrealized Loss 40   49
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3 0 $ 0  
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]      
Due in one year or less 9    
Due in 1 to 5 years 321    
Due in 5 to 10 years 258    
Due after 10 years 282    
Total 870    
Debt Securities, Available-for-sale, Unrealized Gain 1,400    
Debt Securities, Available-for-sale, Unrealized Loss 40   49
Interest Rate Swap      
Nuclear decommissinoning fund [Abstract]      
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net 3    
Fair Value Measured on a Recurring Basis | Cost      
Nuclear decommissinoning fund [Abstract]      
Decommissioning Fund Investments 2,160 [1]   2,130 [2]
Fair Value Measured on a Recurring Basis | Cost | Cash equivalents      
Nuclear decommissinoning fund [Abstract]      
Cash equivalents 49 [1]   39 [2]
Fair Value Measured on a Recurring Basis | Cost | Commingled funds      
Nuclear decommissinoning fund [Abstract]      
Alternative investment [2]     703
Investments, Fair Value Disclosure [1] 703    
Fair Value Measured on a Recurring Basis | Cost | Debt securities      
Nuclear decommissinoning fund [Abstract]      
Debt securities 879 [1]   866 [2]
Fair Value Measured on a Recurring Basis | Cost | Equity securities      
Nuclear decommissinoning fund [Abstract]      
Equity Securities, FV-NI 529 [1]   522 [2]
Fair Value Measured on a Recurring Basis | Fair Value      
Nuclear decommissinoning fund [Abstract]      
Alternative investment 1,015 [1]   1,025 [2]
Decommissioning Fund Investments 3,491 [1]   3,494 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Cash equivalents      
Nuclear decommissinoning fund [Abstract]      
Cash equivalents 49 [1]   39 [2]
Alternative investment 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Commingled funds      
Nuclear decommissinoning fund [Abstract]      
Alternative investment 1,015 [1]   1,025 [2]
Investments, Fair Value Disclosure 1,015    
Fair Value Measured on a Recurring Basis | Fair Value | Debt securities      
Nuclear decommissinoning fund [Abstract]      
Debt securities 870 [1]   846 [2]
Alternative investment 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Equity securities      
Nuclear decommissinoning fund [Abstract]      
Equity Securities, FV-NI 1,557 [1]   1,584 [2]
Alternative investment 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1      
Nuclear decommissinoning fund [Abstract]      
Decommissioning Fund Investments 1,605 [1]   1,622 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Cash equivalents      
Nuclear decommissinoning fund [Abstract]      
Cash equivalents 49 [1]   39 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Commingled funds      
Nuclear decommissinoning fund [Abstract]      
Alternative investment [2]     0
Investments, Fair Value Disclosure [1] 0    
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Debt securities      
Nuclear decommissinoning fund [Abstract]      
Debt securities 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 1 | Equity securities      
Nuclear decommissinoning fund [Abstract]      
Equity Securities, FV-NI 1,556 [1]   1,583 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2      
Nuclear decommissinoning fund [Abstract]      
Decommissioning Fund Investments 857 [1]   833 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Cash equivalents      
Nuclear decommissinoning fund [Abstract]      
Cash equivalents 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Commingled funds      
Nuclear decommissinoning fund [Abstract]      
Alternative investment [2]     0
Investments, Fair Value Disclosure [1] 0    
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Debt securities      
Nuclear decommissinoning fund [Abstract]      
Debt securities 856 [1]   832 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 2 | Equity securities      
Nuclear decommissinoning fund [Abstract]      
Equity Securities, FV-NI 1 [1]   1 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3      
Nuclear decommissinoning fund [Abstract]      
Decommissioning Fund Investments 14 [1]   14 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Cash equivalents      
Nuclear decommissinoning fund [Abstract]      
Cash equivalents 0 [1]   0 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Commingled funds      
Nuclear decommissinoning fund [Abstract]      
Alternative investment [2]     0
Investments, Fair Value Disclosure [1] 0    
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Debt securities      
Nuclear decommissinoning fund [Abstract]      
Debt securities 14 [1]   14 [2]
Fair Value Measured on a Recurring Basis | Fair Value | Level 3 | Equity securities      
Nuclear decommissinoning fund [Abstract]      
Equity Securities, FV-NI $ 0 [1]   $ 0 [2]
[1] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $241 million of equity method investments and $156 million of rabbi trust assets and other miscellaneous investments.
[2] Reported in nuclear decommissioning fund and other investments on the consolidated balance sheets, which also includes $246 million of equity method investments and $156 million of rabbi trust assets and other miscellaneous investments.