v3.26.1
Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Detail)
$ in Millions
 6 Months Ended
Jun. 30, 2026
USD ($)
$ / MMBTU
Jun. 30, 2026
USD ($)
$ / MWh
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value of Derivative Assets $ 1,179 $ 1,179 $ 1,179 $ 958
Fair Value of Derivative Liabilities 461 461 461 245
Virginia Electric and Power Company        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value of Derivative Assets 455 455 455 482
Fair Value of Derivative Liabilities 111 111 111 31
Fair Value, Measurements, Recurring        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Total assets 9,173 9,173 9,173 7,889
Total liabilities 461 461 461 245
Fair Value, Measurements, Recurring | Virginia Electric and Power Company        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Total assets 4,659 4,659 4,659 4,064
Total liabilities 111 111 111 31
Fair Value, Measurements, Recurring | Commodity Contract        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value of Derivative Assets 1,126 1,126 1,126 729
Fair Value of Derivative Liabilities 392 392 392 216
Fair Value, Measurements, Recurring | Commodity Contract | Virginia Electric and Power Company        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value of Derivative Assets 419 419 419 257
Fair Value of Derivative Liabilities 43 43 43 13
Fair Value, Measurements, Recurring | Level 3        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Total assets 1,002 1,002 1,002 642
Total liabilities 72 72 72 15
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Total assets 348 348 348 208
Total liabilities 33 33 33 0
Fair Value, Measurements, Recurring | Level 3 | Commodity Contract        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Fair Value of Derivative Assets 1,002 1,002 1,002 642
Fair Value of Derivative Liabilities 72 72 72 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 348 348 348 208
Fair Value of Derivative Liabilities 33 33 33 $ 0
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] 61 61 61  
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] $ 61 61 61  
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] 12      
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] 3      
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 [1],[2] $ 278 278 278  
Fair Value of Derivative Liabilities [2] 33 33 33  
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 [1],[2] 278 278 278  
Fair Value of Derivative Liabilities [2] $ 33 $ 33 33  
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],[2]   2    
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],[2]   2    
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],[2]   32    
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],[2]   32    
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 [2],[3] 15 [1] 15    
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],[2],[3]   15    
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 [1],[2] $ 288 $ 288 288  
Fair Value of Derivative Liabilities [2] $ 39 $ 39 39  
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],[2]   30    
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],[2]   124    
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 [2],[3] 59 [1] 67    
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] $ 375 $ 375 375  
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] $ 9 $ 9 $ 9  
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] 2      
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]     80.00%  
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]     20.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Minimum | Assets | Credit Spread        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Credit Spread (percentage) [1],[5]     0.00%  
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 [2] (9)      
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 [2] (9)      
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] 20      
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] 20      
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]     3.00%  
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]     74.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Maximum | Assets | Credit Spread        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Credit Spread (percentage) [1],[5]     3.00%  
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] 8      
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]     65.00%  
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]     50.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Natural Gas | Weighted Average | Assets | Credit Spread        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Credit Spread (percentage) [1],[3],[5]     2.00%  
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | FTRs | Maximum | Liabilities | Market Price        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Market Price | $ / MMBTU [2] 32      
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | FTRs | Maximum | Liabilities | Market Price | Virginia Electric and Power Company        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Market Price | $ / MMBTU [2] 32      
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Electricity | Minimum | Liabilities | Market Price        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Market Price | $ / MMBTU [2] 34      
Fair Value, Measurements, Recurring | Level 3 | Option Model | Commodity Contract | Electricity | Maximum | Liabilities | Market Price        
Fair Value, Option, Quantitative Disclosures [Line Items]        
Market Price | $ / MMBTU [2] 187      
[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.
[5] Represents credit spreads unrepresented in published markets.