Trust Investments (Narrative) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) Facility	Dec. 31, 2023 USD ($)
Schedule of Trust Investments [Line Items]
Number of Nuclear Facilities | Facility	5
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
NDT Fund Foreign Currency	$ 1	$ 1
Debt Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
After tax amount of net unrealized gains (losses) recognized in AOCI	(67)
Debt Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
After tax amount of net unrealized gains (losses) recognized in AOCI	(23)
Equity Securities [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Trust Investments [Line Items]
Unrealized Gains (Losses) on Equity Securities still held	92
Equity Securities [Member] | Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Unrealized Gains (Losses) on Equity Securities still held	$ 1