Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2023 USD ($) $ / MWh $ / MMBTU		Dec. 31, 2022 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		$ 1,350		$ 2,176
Fair Value of Derivative Liabilities		697		1,404
Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		298		882
Fair Value of Derivative Liabilities		316		456
Fair Value, Measurements, Recurring
Fair Value, Option, Quantitative Disclosures [Line Items]
Total assets		7,865		7,782
Total liabilities		697		1,404
Fair Value, Measurements, Recurring | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Total assets		3,770		3,902
Total liabilities		316		456
Fair Value, Measurements, Recurring | Commodity Contract
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		550		769
Fair Value of Derivative Liabilities		299		926
Fair Value, Measurements, Recurring | Commodity Contract | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		117		268
Fair Value of Derivative Liabilities		232		348
Fair Value, Measurements, Recurring | Level 3
Fair Value, Option, Quantitative Disclosures [Line Items]
Total assets		225	[1]	437
Total liabilities		139	[1]	15
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Total assets		21	[1]	236
Total liabilities		137	[1]	15
Fair Value, Measurements, Recurring | Level 3 | Commodity Contract
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		225		437
Fair Value of Derivative Liabilities		139		15
Fair Value, Measurements, Recurring | Level 3 | Commodity Contract | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets		21		236
Fair Value of Derivative Liabilities		137		$ 15
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Liabilities	[1],[2]	14
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Liabilities	[1],[2]	$ 14
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Minimum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	(2)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Minimum | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	(2)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Maximum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	3
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Maximum | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	3
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Weighted Average | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2],[3]	4
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Weighted Average | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2],[3]	4
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2],[3]	(1)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Natural Gas | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2],[3]	(1)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1]	$ 3
Fair Value of Derivative Liabilities	[1]	123
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1]	3
Fair Value of Derivative Liabilities	[1]	$ 123
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Minimum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	1
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Minimum | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	(1)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Minimum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	1
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Minimum | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	(1)
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Maximum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	5
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Maximum | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	5
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Maximum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	7
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Maximum | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	7
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Weighted Average | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[3]	2
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Weighted Average | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1],[3]	2
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1],[3]	2
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | FTRs | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1],[3]	2
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1]	$ 152
Fair Value of Derivative Liabilities	[1]	$ 2
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Minimum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	27
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Minimum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	40
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Maximum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	121
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Maximum | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MWh	[1]	127
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Weighted Average | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[3]	47
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow | Commodity Contract | Electricity | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[3]	62
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1],[2]	$ 70
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value of Derivative Assets	[1],[2]	$ 18
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	1
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	1
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Assets | Price Volatility
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[4]	3.00%
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Assets | Price Volatility | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[4]	11.00%
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Market Price
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	7
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Market Price | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Market Price | $ / MMBTU	[1],[2]	7
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Price Volatility
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[4]	76.00%
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Price Volatility | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[4]	64.00%
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Weighted Average | Assets | Price Volatility
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[3],[4]	45.00%
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Weighted Average | Assets | Price Volatility | Virginia Electric and Power Company
Fair Value, Option, Quantitative Disclosures [Line Items]
Price volatility (percentage)	[3],[4]	53.00%

[1] Represents market prices beyond defined terms for Levels 1 and 2.

[2] Includes basis.

[3] Averages weighted by volume.

[4] Represents volatilities unrepresented in published markets.