Investments (Fair Value of Fixed Income Securities by Contractual Maturity) (Detail) $ in Millions	Sep. 30, 2024 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	$ 27
Due after one year through five years	572
Due after five years through ten years	459
Due after ten years	1,218
Total	2,276
Virginia Electric and Power Company
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less	18
Due after one year through five years	299
Due after five years through ten years	273
Due after ten years	769
Total	$ 1,359