Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Mar. 31, 2022 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 274
Due after one year through five years	610
Due after five years through ten years	596
Due after ten years	837
Total	2,317
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	83
Due after one year through five years	302
Due after five years through ten years	358
Due after ten years	374
Total	$ 1,117