Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Sep. 30, 2022 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 122
Due after one year through five years	512
Due after five years through ten years	453
Due after ten years	729
Total	1,816
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	64
Due after one year through five years	277
Due after five years through ten years	301
Due after ten years	381
Total	$ 1,023