Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Dec. 31, 2021 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 331
Due after one year through five years	642
Due after five years through ten years	630
Due after ten years	868
Total	2,471
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	78
Due after one year through five years	335
Due after five years through ten years	361
Due after ten years	408
Total	$ 1,182