Property, Plant and Equipment (Share of Jointly-Owned Power Stations) (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Bath Country Pumped Storage Station
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	60.00%	[1]
Plant in service	$ 1,064	[1]
Accumulated depreciation	(688)	[1]
Plant under construction	$ 3	[1]
North Anna
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	88.40%	[1]
Plant in service	$ 2,587	[1]
Accumulated depreciation	(1,359)	[1]
Nuclear fuel	793	[1]
Accumulated amortization of nuclear fuel	(661)	[1]
Plant under construction	$ 158	[1]
Clover Power Station
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	50.00%	[1]
Plant in service	$ 609	[1]
Accumulated depreciation	(260)	[1]
Plant under construction	$ 1	[1]
Millstone Unit
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	93.50%	[2]
Plant in service	$ 1,292	[2]
Accumulated depreciation	(482)	[2]
Nuclear fuel	573	[2]
Accumulated amortization of nuclear fuel	(444)	[2]
Plant under construction	$ 78	[2]
Summer Unit
Jointly Owned Utility Plant Interests [Line Items]
Ownership interest	66.70%	[2]
Plant in service	$ 1,519	[2]
Accumulated depreciation	(676)	[2]
Nuclear fuel	575	[2]
Accumulated amortization of nuclear fuel	(354)	[2]
Plant under construction	$ 61	[2]

[1] Units jointly owned by Virginia Power.

[2] Unit jointly owned by Dominion Energy.