Regulatory Matters - Schedule of Developments for Significant Riders Associated with Virginia Power Projects (Detail) - Virginia Electric and Power Company - Rider US-3 $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Public Utilities General Disclosures [Line Items]
Application Date	2019-07
Approval Date	March 2020
Rate Year Beginning	2020-06
Total Revenue Requirement (millions)	$ 28
Increase (decrease) in revenue requirement	$ 18