Operating Revenue (Schedule of Aggregate Amount of Transaction Price Allocated To Fixed-price Performance Obligations That Unsatisfied At End of Reporting Period And Expected To be Recognized) (Detail) $ in Millions	Mar. 31, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts	$ 662	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period	9 months
Revenue, expected to be recognized on multi-year contracts	$ 51	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, expected to be recognized on multi-year contracts	$ 61	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, expected to be recognized on multi-year contracts	$ 54	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period	2026 years
Revenue, expected to be recognized on multi-year contracts	$ 48	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period	1 year
Revenue, expected to be recognized on multi-year contracts	$ 46	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, expected to be recognized on multi-year contracts, period
Revenue, expected to be recognized on multi-year contracts	$ 402	[1]

[1] Includes no amounts for Virginia Power