v3.25.2
Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Detail)
$ in Millions
 6 Months Ended
Jun. 30, 2025
USD ($)
$ / MWh
$ / MMBTU
Dec. 31, 2024
USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets $ 746 $ 1,399
Fair Value of Derivative Liabilities 204 512
Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets 321 375
Fair Value of Derivative Liabilities 63 225
Fair Value, Measurements, Recurring    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Total assets 8,998 9,259
Total liabilities 204 512
Fair Value, Measurements, Recurring | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Total assets 4,714 4,563
Total liabilities 63 225
Fair Value, Measurements, Recurring | Commodity Contract    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets 519 494
Fair Value of Derivative Liabilities 129 123
Fair Value, Measurements, Recurring | Commodity Contract | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets 206 115
Fair Value of Derivative Liabilities 38 33
Fair Value, Measurements, Recurring | Level 3    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Total assets 436 399
Total liabilities 22 15
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Total assets 183 70
Total liabilities 4 2
Fair Value, Measurements, Recurring | Level 3 | Commodity Contract    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets 436 399
Fair Value of Derivative Liabilities 22 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 183 70
Fair Value of Derivative Liabilities 4 $ 2
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Natural Gas | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [1],[2] 2  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Natural Gas | Market Price | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [1],[2] $ 2  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Natural Gas | Minimum | Assets | 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 | Assets | 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 | Assets | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2] 4  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | 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] 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] (1)  
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] (1)  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | FTRs | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [2] $ 173  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | FTRs | Market Price | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [2] $ 173  
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 [2] (3)  
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 [2] (3)  
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 [2] 15  
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 [2] 15  
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 | $ / MWh [2],[3] 7  
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 [2],[3] 7  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Electricity | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [2] $ 185  
Fair Value of Derivative Liabilities [2] $ 18  
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 [2] 28  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Electricity | Minimum | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MWh [2] 28  
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 [2] 111  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Electricity | Maximum | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MWh [2] 119  
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 | $ / MWh [2],[3] 49  
Fair Value, Measurements, Recurring | Level 3 | Discounted cash flow | Commodity Contract | Electricity | Weighted Average | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MWh [2],[3] 58  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [1],[2] $ 76  
Fair Value of Derivative Liabilities [1],[2] 4  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Market Price | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Fair Value of Derivative Assets [1],[2] 8  
Fair Value of Derivative Liabilities [1],[2] $ 4  
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] 3  
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) [1],[4] 11.00%  
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) [1],[4] 19.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2] (2)  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | 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 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2] 9  
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] 9  
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) [1],[4] 72.00%  
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) [1],[4] 70.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2] 3  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | 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 | Option Model | 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 | Option Model | 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] 6  
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) [1],[3],[4] 43.00%  
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) [1],[3],[4] 43.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Weighted Average | Liabilities | Market Price    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2],[3] (1)  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Weighted Average | Liabilities | Market Price | Virginia Electric and Power Company    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Market Price | $ / MMBTU [1],[2],[3] (1)  
[1] Includes basis.
[2] Represents market prices beyond defined terms for Levels 1 and 2.
[3] Averages weighted by volume.
[4] Represents volatilities unrepresented in published markets.