Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Derivatives Fair Value [Line Items]
Total current derivative assets	$ 490	$ 335
Total noncurrent derivative assets	689	623
Total derivative assets	1,179	958
Total current derivative liabilities	226	111
Total noncurrent derivative liabilities	235	134
Total derivative liabilities	461	245
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	310	212
Total noncurrent derivative assets	145	270
Total derivative assets	455	482
Total current derivative liabilities	50	22
Total noncurrent derivative liabilities	61	9
Total derivative liabilities	111	31
Designated as Hedging Instrument \| Interest Rate Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	0	15
Total noncurrent derivative assets	37	184
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	60	9
Designated as Hedging Instrument \| Interest Rate Contract \| Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	0	15
Total noncurrent derivative assets	34	182
Total current derivative liabilities	0	0
Total noncurrent derivative liabilities	60	8
Fair Value - Derivatives not under Hedge Accounting \| Commodity Contract
Derivatives Fair Value [Line Items]
Total current derivative assets	486	295
Total noncurrent derivative assets	640	434
Total current derivative liabilities	218	98
Total noncurrent derivative liabilities	174	118
Fair Value - Derivatives not under Hedge Accounting \| Commodity Contract \| Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Total current derivative assets	308	172
Total noncurrent derivative assets	111	85
Total current derivative liabilities	42	12
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	2	0
Total noncurrent derivative assets	12	2
Total current derivative liabilities	0	3
Total noncurrent derivative liabilities	1	7
Fair Value - Derivatives not under Hedge Accounting \| Foreign currency exchange rate
Derivatives Fair Value [Line Items]
Total current derivative assets	2	25
Total noncurrent derivative assets	0	3
Total current derivative liabilities	8	10
Total noncurrent derivative liabilities	0	0
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	2	25
Total noncurrent derivative assets	0	3
Total current derivative liabilities	8	10
Total noncurrent derivative liabilities	$ 0	$ 0