Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivatives Fair Value [Line Items]
Total current derivative assets	$ 545	$ 753
Total noncurrent derivative assets	615	597
Total derivative assets	1,160	1,350
Total current derivative liabilities	107	376
Total noncurrent derivative liabilities	74	321
Total derivative liabilities	181	697
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	135	234
Total noncurrent derivative assets	64	64
Total derivative assets	199	298
Total current derivative liabilities	80	244
Total noncurrent derivative liabilities	32	72
Total derivative liabilities	112	316
Commodity Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	235	312
Total noncurrent derivative assets	215	238
Total current derivative liabilities	81	244
Total noncurrent derivative liabilities	28	55
Commodity Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	130	91
Total noncurrent derivative assets	16	26
Total current derivative liabilities	54	188
Total noncurrent derivative liabilities	6	44
Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	305	441
Total noncurrent derivative assets	397	359
Total current derivative liabilities	0	121
Total noncurrent derivative liabilities	20	238
Interest Rate Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	143
Total noncurrent derivative assets	45	38
Total current derivative liabilities	0	45
Total noncurrent derivative liabilities	0	0
Foreign currency exchange rate
Derivatives Fair Value [Line Items]
Total current derivative assets	5
Total noncurrent derivative assets	3
Total current derivative liabilities	26	11
Total noncurrent derivative liabilities	26	28
Foreign currency exchange rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	5
Total noncurrent derivative assets	3
Total current derivative liabilities	26	11
Total noncurrent derivative liabilities	26	28
Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Total current derivative assets	0	143
Total noncurrent derivative assets	45	38
Total derivative assets	45	181
Total current derivative liabilities	0	45
Total noncurrent derivative liabilities	0	0
Total derivative liabilities	0	45
Designated as Hedging Instrument | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	143
Total noncurrent derivative assets	45	38
Total derivative assets	45	181
Total current derivative liabilities	0	45
Total noncurrent derivative liabilities	0	0
Total derivative liabilities	0	45
Designated as Hedging Instrument | Commodity Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	0	0
Total noncurrent derivative assets	0	0
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	0	0
Designated as Hedging Instrument | Commodity Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	0
Total noncurrent derivative assets	0	0
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	0	0
Designated as Hedging Instrument | Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	0	143
Total noncurrent derivative assets	45	38
Total current derivative liabilities	0	45
Total noncurrent derivative liabilities	0	0
Designated as Hedging Instrument | Interest Rate Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	143
Total noncurrent derivative assets	45	38
Total current derivative liabilities	0	45
Total noncurrent derivative liabilities	0	0
Designated as Hedging Instrument | Foreign currency exchange rate
Derivatives Fair Value [Line Items]
Total current derivative assets	0
Total noncurrent derivative assets	0
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	0	0
Designated as Hedging Instrument | Foreign currency exchange rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0
Total noncurrent derivative assets	0
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	0	0
Fair Value - Derivatives not under Hedge Accounting
Derivatives Fair Value [Line Items]
Total current derivative assets	545	610
Total noncurrent derivative assets	570	559
Total derivative assets	1,115	1,169
Total current derivative liabilities	107	331
Total noncurrent derivative liabilities	74	321
Total derivative liabilities	181	652
Fair Value - Derivatives not under Hedge Accounting | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	135	91
Total noncurrent derivative assets	19	26
Total derivative assets	154	117
Total current derivative liabilities	80	199
Total noncurrent derivative liabilities	32	72
Total derivative liabilities	112	271
Fair Value - Derivatives not under Hedge Accounting | Commodity Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	235	312
Total noncurrent derivative assets	215	238
Total current derivative liabilities	81	244
Total noncurrent derivative liabilities	28	55
Fair Value - Derivatives not under Hedge Accounting | Commodity Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	130	91
Total noncurrent derivative assets	16	26
Total current derivative liabilities	54	188
Total noncurrent derivative liabilities	6	44
Fair Value - Derivatives not under Hedge Accounting | Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	305	298
Total noncurrent derivative assets	352	321
Total current derivative liabilities	0	76
Total noncurrent derivative liabilities	20	238
Fair Value - Derivatives not under Hedge Accounting | Interest Rate Contract | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	0
Total noncurrent derivative assets	0	0
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	0	0
Fair Value - Derivatives not under Hedge Accounting | Foreign currency exchange rate
Derivatives Fair Value [Line Items]
Total current derivative assets	5
Total noncurrent derivative assets	3
Total current derivative liabilities	26	11
Total noncurrent derivative liabilities	26	28
Fair Value - Derivatives not under Hedge Accounting | Foreign currency exchange rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	5
Total noncurrent derivative assets	3
Total current derivative liabilities	26	11
Total noncurrent derivative liabilities	$ 26	$ 28