Related-Party Transactions (Narrative) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Derivative assets	$ 1,209,000,000		$ 613,000,000
Derivative liabilities	1,314,000,000		868,000,000
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Derivative assets	404,000,000		300,000,000
Derivative liabilities	508,000,000		470,000,000
Payable to affiliates	235,000,000		699,000,000	[1]
Outstanding borrowings, net of repayments, under money pool for non-regulated subsidiaries	$ 0		0
Issuance of common stock to Dominion	0	0
Virginia Electric and Power Company | Pension Benefits | Amounts Associated With Dominion Pension Plan
Related Party Transaction [Line Items]
Amounts due to Dominion, noncurrent	$ 540,000,000		522,000,000
Payment to be paid to Dominion, in 2022	175,000,000
Virginia Electric and Power Company | Medical Coverage for Local retirees | Amounts Associated with the Dominion Retiree Health and Welfare Plan
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent	453,000,000		431,000,000
Virginia Electric and Power Company | Affiliated Entity
Related Party Transaction [Line Items]
Derivative assets	64,000,000		29,000,000
Derivative liabilities	1,000,000		6,000,000
Virginia Electric and Power Company | Principal Owner | Short-Term Borrowing Arrangements
Related Party Transaction [Line Items]
Payable to affiliates	$ 235,000,000		$ 699,000,000

[1] Virginia Power’s Consolidated Balance Sheet at December 31, 2021 has been derived from the audited Consolidated Balance Sheet at that date.