Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Detail) $ in Millions | 6 Months Ended | |
Jun. 30, 2019USD ($)$ / MMBTU$ / MWh | Dec. 31, 2018USD ($) |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | $ 209 | $ 294 |
Fair Value of Derivative Liabilities | | 626 | 279 |
Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 83 | 93 |
Fair Value of Derivative Liabilities | | 358 | 103 |
Fair Value, Measurements, Recurring | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total assets | | 5,710 | 5,156 |
Total liabilities | | 626 | 279 |
Fair Value, Measurements, Recurring | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total assets | | 2,611 | 2,297 |
Total liabilities | | 358 | 103 |
Fair Value, Measurements, Recurring | Commodity | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 188 | 250 |
Fair Value of Derivative Liabilities | | 69 | 135 |
Fair Value, Measurements, Recurring | Commodity | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 83 | 90 |
Fair Value of Derivative Liabilities | | 26 | 15 |
Fair Value, Measurements, Recurring | Level 3 | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total assets | | 84 | 70 |
Total liabilities | | 9 | 6 |
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total assets | | 81 | 66 |
Total liabilities | | 4 | 6 |
Fair Value, Measurements, Recurring | Level 3 | Derivative Financial Instruments, Liabilities | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total liabilities | | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Assets | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Total assets | | 81 | |
Fair Value, Measurements, Recurring | Level 3 | Commodity | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 84 | 70 |
Fair Value of Derivative Liabilities | | 9 | 6 |
Fair Value, Measurements, Recurring | Level 3 | Commodity | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 81 | 66 |
Fair Value of Derivative Liabilities | | 4 | $ 6 |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | 7 | |
Fair Value of Derivative Liabilities | | 3 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Derivative Financial Instruments, Liabilities | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Liabilities | | 3 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Assets | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | $ 7 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Minimum | Derivative Financial Instruments, Liabilities | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | (4) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Minimum | Derivative Financial Instruments, Liabilities | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | (4) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Minimum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | (1) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Minimum | Assets | Market Price [Member] | 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 [Member] | FTRs [Member] | Commodity | Maximum | Derivative Financial Instruments, Liabilities | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Maximum | Derivative Financial Instruments, Liabilities | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Maximum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Maximum | Assets | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Weighted Average | Derivative Financial Instruments, Liabilities | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1] | 0 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Weighted Average | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1],[2] | 1 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | FTRs [Member] | Commodity | Weighted Average | Assets | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MWh | [1],[2] | 1 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | [3] | $ 76 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Assets | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | [3] | $ 74 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Minimum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | (2) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Minimum | Assets | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | (2) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Maximum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 6 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Maximum | Assets | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 3 | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Weighted Average | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1],[2] | (1) | |
Fair Value, Measurements, Recurring | Level 3 | Discounted Cash Flow [Member] | Natural Gas | Commodity | Weighted Average | Assets | Market Price [Member] | 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 [Member] | Natural Gas | Physical Options [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Assets | | $ 1 | |
Fair Value of Derivative Liabilities | | 6 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Derivative Financial Instruments, Liabilities | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Fair Value of Derivative Liabilities | | $ 1 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Derivative Financial Instruments, Liabilities | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 1 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Derivative Financial Instruments, Liabilities | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 1 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 2.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 20.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 2 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Minimum | Assets | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 2.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Derivative Financial Instruments, Liabilities | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 8 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Derivative Financial Instruments, Liabilities | Market Price [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 7 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 71.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 71.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1] | 12 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Maximum | Assets | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [4] | 34.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1],[2] | 3 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Derivative Financial Instruments, Liabilities | Market Price [Member] | 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 [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [2],[4] | 29.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Derivative Financial Instruments, Liabilities | Price Volatility [Member] | Virginia Electric and Power Company | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [2],[4] | 38.00% | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Assets | Market Price [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Market Price | $ / MMBTU | [1],[2] | 4 | |
Fair Value, Measurements, Recurring | Level 3 | Option Model [Member] | Natural Gas | Physical Options [Member] | Weighted Average | Assets | Price Volatility [Member] | | | |
Fair Value, Option, Quantitative Disclosures [Line Items] | | | |
Price volatility (percentage) | [2],[4] | 19.00% | |
| |
[1] | Represents market prices beyond defined terms for Levels 1 and 2. | |
[2] | Averages weighted by volume. | |
[3] | Includes basis. | |
[4] | Represents volatilities unrepresented in published markets. | |