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Trust Investments (Amount Of Available-For-Sale Debt Securities By Maturity Periods) (Detail)
$ in Millions
Mar. 31, 2023
USD ($)
Nuclear Decommissioning Trust (NDT) Fund [Member]  
Schedule of Trust Investments [Line Items]  
Total Available-for-Sale Debt Securities $ 1,203
Rabbi Trust [Member]  
Schedule of Trust Investments [Line Items]  
Total Available-for-Sale Debt Securities 170
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]  
Schedule of Trust Investments [Line Items]  
Less than one year 17
1 - 5 years 303
6 - 10 years 219
11 - 15 years 64
16 - 20 years 100
Over 20 years 500
Debt Securities [Member] | Rabbi Trust [Member]  
Schedule of Trust Investments [Line Items]  
Less than one year 2
1 - 5 years 28
6 - 10 years 23
11 - 15 years 10
16 - 20 years 16
Over 20 years $ 91