Goodwill and Intangible Assets (Components of Intangible Assets) (Detail) - Software, Licenses and Other - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	$ 1,459	$ 1,295
Accumulated Amortization	[1]	675	530
Virginia Electric and Power Company
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	685	482
Accumulated Amortization	[1]	$ 290	$ 148

[1] Includes $158M of RGGI allowances purchased and consumed in 2021, with deferral to a regulatory asset.