Trust Investments (Amount Of Available-For-Sale Debt Securities By Maturity Periods) (Detail) $ in Millions	Jun. 30, 2023 USD ($)
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	$ 1,192
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Total Available-for-Sale Debt Securities	164
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Less than one year	20
1 - 5 years	293
6 - 10 years	220
11 - 15 years	66
16 - 20 years	101
Over 20 years	492
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Less than one year	7
1 - 5 years	25
6 - 10 years	20
11 - 15 years	10
16 - 20 years	14
Over 20 years	$ 88