Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 185
Due after one year through five years	509
Due after five years through ten years	407
Due after ten years	981
Total	2,082
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	140
Due after one year through five years	250
Due after five years through ten years	236
Due after ten years	588
Total	$ 1,214