Regulatory Matters - Schedule of Additional Significant Riders Associated with Virginia Power Projects (Parenthetical) (Detail) - Virginia Electric and Power Company $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Rider SNA
Public Utilities General Disclosures [Line Items]
Total revenue requirement	$ 107
Rider T1
Public Utilities General Disclosures [Line Items]
Total revenue requirement	706
Rider U
Public Utilities General Disclosures [Line Items]
Total revenue requirement	95
Virginia Regulation | Previous Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment	60
Virginia Regulation | Rider SNA | Operating Segments | Transmission Component Of Virginia Powers
Public Utilities General Disclosures [Line Items]
Projected capital investment	1,200
Virginia Regulation | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement	224
Virginia Regulation | Rider T1 | Operating Segments | Transmission Component Of Virginia Powers
Public Utilities General Disclosures [Line Items]
Total revenue requirement	482
Virginia Regulation | Rider U | Previous Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment	$ 35