Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivatives Fair Value [Line Items]
Total current derivative assets	$ 332	$ 436
Total noncurrent derivative assets	414	963
Total derivative assets	746	1,399
Total current derivative liabilities	86	207
Total noncurrent derivative liabilities	118	305
Total derivative liabilities	204	512
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	230	248
Total noncurrent derivative assets	91	127
Total derivative assets	321	375
Total current derivative liabilities	38	139
Total noncurrent derivative liabilities	25	86
Total derivative liabilities	63	225
Designated as Hedging Instrument \| Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	6	137
Total noncurrent derivative assets	65	93
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	31	0
Designated as Hedging Instrument \| Interest Rate Contract \| Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	6	137
Total noncurrent derivative assets	65	93
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	16	0
Fair Value - Derivatives not under Hedge Accounting \| Commodity Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	281	171
Total noncurrent derivative assets	238	323
Total current derivative liabilities	82	78
Total noncurrent derivative liabilities	47	45
Fair Value - Derivatives not under Hedge Accounting \| Commodity Contract \| Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	192	84
Total noncurrent derivative assets	14	31
Total current derivative liabilities	37	32
Total noncurrent derivative liabilities	1	1
Fair Value - Derivatives not under Hedge Accounting \| Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	13	101
Total noncurrent derivative assets	99	544
Total current derivative liabilities	3	22
Total noncurrent derivative liabilities	32	175
Fair Value - Derivatives not under Hedge Accounting \| Foreign currency exchange rate
Derivatives Fair Value [Line Items]
Total current derivative assets	32	27
Total noncurrent derivative assets	12	3
Total current derivative liabilities	1	107
Total noncurrent derivative liabilities	8	85
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	32	27
Total noncurrent derivative assets	12	3
Total current derivative liabilities	1	107
Total noncurrent derivative liabilities	$ 8	$ 85