Long-Term Debt (Based on Stated Maturity Dates Rather than Early Redemption Dates that Could be Elected by Instrument Holders) (Detail) $ in Millions	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
2022	$ 807
2023	2,851
2024	3,636
2025	2,019
2026	2,277
Thereafter	26,104
Total	$ 37,694
Weighted- average coupon, 2022	2.79%
Weighted- average coupon, 2023	1.89%
Weighted- average coupon, 2024	2.20%
Weighted- average coupon, 2025	3.01%
Weighted- average coupon, 2026	2.82%
Weighted- average coupon, Thereafter	4.26%
Unsecured senior notes
Debt Instrument [Line Items]
2022	$ 650
2023	2,700
2024	690
2025	2,000
2026	2,257
Thereafter	20,779
Total	29,076
Tax-exempt financings
Debt Instrument [Line Items]
Thereafter	775
Total	775
Term loans
Debt Instrument [Line Items]
2022	151
2023	134
2024	2,215
Total	2,500
First mortgage bonds
Debt Instrument [Line Items]
Thereafter	3,634
Total	3,634
Secured senior notes
Debt Instrument [Line Items]
2022	6
2023	17
2024	31
2025	19
2026	20
Thereafter	221
Total	314
Unsecured junior subordinated notes payable to affiliated trusts
Debt Instrument [Line Items]
Thereafter	10
Total	10
Unsecured junior subordinated notes
Debt Instrument [Line Items]
2024	700
Total	700
Enhanced Junior Subordinated Notes
Debt Instrument [Line Items]
Thereafter	685
Total	685
Virginia Electric and Power Company
Debt Instrument [Line Items]
2022	300
2023	700
2024	350
2025	350
2026	1,150
Thereafter	11,013
Total	$ 13,863
Weighted- average coupon, 2022	3.45%
Weighted- average coupon, 2023	2.75%
Weighted- average coupon, 2024	3.45%
Weighted- average coupon, 2025	3.10%
Weighted- average coupon, 2026	3.08%
Weighted- average coupon, Thereafter	4.16%
Virginia Electric and Power Company | Unsecured senior notes
Debt Instrument [Line Items]
2022	$ 300
2023	700
2024	350
2025	350
2026	1,150
Thereafter	10,388
Total	13,238
Virginia Electric and Power Company | Tax-exempt financings
Debt Instrument [Line Items]
Thereafter	625
Total	$ 625