Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Mar. 31, 2024 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 30
Due after one year through five years	514
Due after five years through ten years	405
Due after ten years	985
Total	1,934
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	16
Due after one year through five years	254
Due after five years through ten years	236
Due after ten years	589
Total	$ 1,095