Leases (Scheduled Maturities of Lease Liabilities) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Maturity of Operating Lease Liabilities
Maturity of Lease Liabilities, Operating, 2020	$ 72
Maturity of Lease Liabilities, Operating, 2021	65
Maturity of Lease Liabilities, Operating, 2022	55
Maturity of Lease Liabilities, Operating, 2023	45
Maturity of Lease Liabilities, Operating, 2024	36
Maturity of Lease Liabilities, Operating, After 2024	582
Maturity of Lease Liabilities, Operating, Total undiscounted lease payments	855
Present value adjustment, Operating	(377)
Present value of lease liabilities, Operating	478
Maturity of Finance Lease Liabilities
Maturity of Lease Liabilities, Finance, 2020	34
Maturity of Lease Liabilities, Finance, 2021	31
Maturity of Lease Liabilities, Finance, 2022	29
Maturity of Lease Liabilities, Finance, 2023	26
Maturity of Lease Liabilities, Finance, 2024	19
Maturity of Lease Liabilities, Finance, After 2024	9
Maturity of Lease Liabilities, Finance, Total undiscounted lease payments	148
Present value adjustment, Finance	(14)
Present value of lease liabilities, Finance	134	$ 39
Virginia Electric And Power Company [Member]
Maturity of Operating Lease Liabilities
Maturity of Lease Liabilities, Operating, 2020	34
Maturity of Lease Liabilities, Operating, 2021	30
Maturity of Lease Liabilities, Operating, 2022	24
Maturity of Lease Liabilities, Operating, 2023	19
Maturity of Lease Liabilities, Operating, 2024	14
Maturity of Lease Liabilities, Operating, After 2024	205
Maturity of Lease Liabilities, Operating, Total undiscounted lease payments	326
Present value adjustment, Operating	(139)
Present value of lease liabilities, Operating	187
Maturity of Finance Lease Liabilities
Maturity of Lease Liabilities, Finance, 2020	4
Maturity of Lease Liabilities, Finance, 2021	4
Maturity of Lease Liabilities, Finance, 2022	4
Maturity of Lease Liabilities, Finance, 2023	3
Maturity of Lease Liabilities, Finance, 2024	3
Maturity of Lease Liabilities, Finance, After 2024	4
Maturity of Lease Liabilities, Finance, Total undiscounted lease payments	22
Present value adjustment, Finance	(3)
Present value of lease liabilities, Finance	19
Dominion Energy Gas Holdings L L C [Member]
Maturity of Operating Lease Liabilities
Maturity of Lease Liabilities, Operating, 2020	7
Maturity of Lease Liabilities, Operating, 2021	6
Maturity of Lease Liabilities, Operating, 2022	5
Maturity of Lease Liabilities, Operating, 2023	4
Maturity of Lease Liabilities, Operating, 2024	3
Maturity of Lease Liabilities, Operating, After 2024	20
Maturity of Lease Liabilities, Operating, Total undiscounted lease payments	45
Present value adjustment, Operating	(10)
Present value of lease liabilities, Operating	35
Maturity of Finance Lease Liabilities
Maturity of Lease Liabilities, Finance, 2020	2
Maturity of Lease Liabilities, Finance, 2021	1
Maturity of Lease Liabilities, Finance, 2022	1
Maturity of Lease Liabilities, Finance, 2023	1
Maturity of Lease Liabilities, Finance, 2024	1
Maturity of Lease Liabilities, Finance, After 2024	1
Maturity of Lease Liabilities, Finance, Total undiscounted lease payments	7
Present value adjustment, Finance	(1)
Present value of lease liabilities, Finance	$ 6