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Trust Investments (Fair Values And Gross Unrealized Gains And Losses For The Securities Held) (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2023
Dec. 31, 2022
Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Trust Investments, Cost $ 2,142 $ 2,130
Gross Unrealized Gains 341 301
Gross Unrealized Losses (155) (203)
Trust Investments, Fair Value 2,328 [1] 2,228 [2]
NDT Fund Foreign Currency 3 2
Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Trust Investments, Cost 213 213
Gross Unrealized Gains 7 6
Gross Unrealized Losses (30) (36)
Trust Investments, Fair Value 190 183
Total Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,328 1,318
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 5 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (130) (163)
Debt Securities, Available-for-Sale, Fair Value 1,203 1,156
Total Debt Securities [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 200 199
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 0 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (30) (36)
Debt Securities, Available-for-Sale, Fair Value 170 163
Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Equity Securities, Cost 814 812
Equity Securities, Accumulated Gross Unrealized Gain 336 300
Equity Securities, FV-NI, Unrealized Loss (25) (40)
Equity Securities, Fair Value 1,125 1,072
Unrealized Gains (Losses) on Equity Securities still held 56  
Equity Securities [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Unrealized Gains (Losses) on Equity Securities still held 1  
Corporate Debt Obligations [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 593 597
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 2 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (55) (69)
Debt Securities, Available-for-Sale, Fair Value 540 529
Corporate Debt Obligations [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 88 89
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 0 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (12) (15)
Debt Securities, Available-for-Sale, Fair Value 76 74
Government Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 735 721
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 3 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (75) (94)
Debt Securities, Available-for-Sale, Fair Value 663 627
Government Debt Securities [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 112 110
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax 0 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax (18) (21)
Debt Securities, Available-for-Sale, Fair Value 94 89
International Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Equity Securities, Cost 383 336
Equity Securities, Accumulated Gross Unrealized Gain 86 68
Equity Securities, FV-NI, Unrealized Loss (18) (28)
Equity Securities, Fair Value 451 376
Domestic Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
Equity Securities, Cost 431 476
Equity Securities, Accumulated Gross Unrealized Gain 250 232
Equity Securities, FV-NI, Unrealized Loss (7) (12)
Equity Securities, Fair Value 674 696
Domestic Equity Securities [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
Equity Securities, Cost 13 14
Equity Securities, Accumulated Gross Unrealized Gain 7 6
Equity Securities, FV-NI, Unrealized Loss 0 0
Equity Securities, Fair Value 20 $ 20
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]    
Schedule of Trust Investments [Line Items]    
After tax amount of net unrealized gains recognized in AOCI (73)  
Debt Securities [Member] | Rabbi Trust [Member]    
Schedule of Trust Investments [Line Items]    
After tax amount of net unrealized gains recognized in AOCI $ (22)  
[1] The NDT Fund Investments table excludes cash and foreign currency of $3 million as of March 31, 2023, which is part of the NDT Fund.
[2] The NDT Fund Investments table excludes cash and foreign currency of $2 million as of December 31, 2022, which is part of the NDT Fund.