Trust Investments (Amount Of Available-For-Sale Debt Securities By Maturity Periods) (Detail) $ in Millions	Mar. 31, 2024 USD ($)
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	$ 1,212
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	155
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Less than one year	18
1 - 5 years	335
6 - 10 years	204
11 - 15 years	64
16 - 20 years	95
Over 20 years	496
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Less than one year	7
1 - 5 years	26
6 - 10 years	17
11 - 15 years	9
16 - 20 years	18
Over 20 years	$ 78