Trust Investments (Amount Of Available-For-Sale Debt Securities By Maturity Periods) (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	$ 1,141
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	150
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Less than one year	18
1 - 5 years	293
6 - 10 years	212
11 - 15 years	61
16 - 20 years	94
Over 20 years	463
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Less than one year	8
1 - 5 years	26
6 - 10 years	16
11 - 15 years	9
16 - 20 years	17
Over 20 years	$ 74