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Fair Value Measurements (Fair Value, Option, Quantitative Disclosures) (Detail) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) $ / MWh $ / DTH $ / gal | Dec. 31, 2016 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | $ 307 | $ 279
Fair Value of Derivative Liabilities |  | 284 | 155
Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 166 | 194
Fair Value of Derivative Liabilities |  | 66 | 31
Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 32 |
Fair Value of Derivative Liabilities |  | 8 | 11
Fair Value, Measurements, Recurring |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Assets |  | 5,379 | 4,722
Total Liabilities |  | 284 | 155
Fair Value, Measurements, Recurring | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Assets |  | 2,466 | 2,200
Total Liabilities |  | 66 | 31
Fair Value, Measurements, Recurring | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Assets |  | 32 |
Total Liabilities |  | 8 | 11
Fair Value, Measurements, Recurring | Commodity |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 258 | 262
Fair Value of Derivative Liabilities |  | 197 | 96
Fair Value, Measurements, Recurring | Commodity | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 166 | 188
Fair Value of Derivative Liabilities |  | 9 | 10
Fair Value, Measurements, Recurring | Commodity | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Liabilities |  | 6 | 5
Fair Value, Measurements, Recurring | Level 3 |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Assets |  | 157 | 147
Total Liabilities |  | 7 | 8
Fair Value, Measurements, Recurring | Level 3 | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Assets |  | 152 | 145
Total Liabilities |  | 5 | 2
Fair Value, Measurements, Recurring | Level 3 | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Total Liabilities |  | 2 | 2
Fair Value, Measurements, Recurring | Level 3 | Commodity |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 157 | 147
Fair Value of Derivative Liabilities |  | 7 | 8
Fair Value, Measurements, Recurring | Level 3 | Commodity | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 152 | 145
Fair Value of Derivative Liabilities |  | 5 | 2
Fair Value, Measurements, Recurring | Level 3 | Commodity | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Liabilities |  | 2 | $ 2
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 29 |
Fair Value of Derivative Liabilities |  | 5 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | 27 |
Fair Value of Derivative Liabilities |  | $ 5 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity | Liabilities | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | (4) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity | Liabilities | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | (4) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity | Liabilities | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 6 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | FTRs [Member] | Commodity | Liabilities | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 6 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Liabilities |  | $ 2 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Liabilities | Minimum | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 0 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Liabilities | Maximum | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 1 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Liabilities | Weighted Average | Dominion Energy Gas Holdings, LLC |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1],[2] | 1 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Commodity |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Liabilities | [3] | $ 2 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Commodity | Liabilities | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / gal | [1] | 0 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Commodity | Liabilities | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / gal | [1] | 2 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas Liquids [Member] | Commodity | Liabilities | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / gal | [1],[2] | 1 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | (1) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | (1) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 7 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 7 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1],[2] | 2 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Assets | FTRs [Member] | Commodity | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1],[2] | 2 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Commodity |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets | [4] | $ 84 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Commodity | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets | [4] | $ 81 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | (2) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | (2) |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 14 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 7 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1],[2] | 0 |
Fair Value, Measurements, Recurring | Discounted Cash Flow [Member] | Level 3 | Natural Gas | Assets | Commodity | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1],[2] | (1) |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Electricity | Physical Options [Member] |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | $ 43 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Electricity | Physical Options [Member] | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | $ 43 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 22 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 22 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 74 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1] | 74 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1],[2] | 37 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Market Price [Member] | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / MWh | [1],[2] | 37 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 13.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 13.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 63.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 63.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [2],[5] | 33.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Assets | Electricity | Physical Options [Member] | Price Volatility [Member] | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [2],[5] | 33.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Physical Options [Member] |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | $ 1 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Physical Options [Member] | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Fair Value of Derivative Assets |  | $ 1 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 2 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 2 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 7 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1] | 7 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1],[2] | 3 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Market Price [Member] | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Market Price | $ / DTH | [1],[2] | 3 |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Minimum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 26.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Minimum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 26.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Maximum |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 54.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Maximum | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [5] | 54.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Weighted Average |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [2],[5] | 33.00% |
Fair Value, Measurements, Recurring | Option Model [Member] | Level 3 | Natural Gas | Assets | Physical Options [Member] | Price Volatility [Member] | Weighted Average | Virginia Electric and Power Company |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Price volatility (percentage) | [2],[5] | 33.00% |
[1] | Represents market prices beyond defined terms for Levels 1 and 2.
[2] | Averages weighted by volume.
[3] | Includes NGLs and oil.
[4] | Includes basis.
[5] | Represents volatilities unrepresented in published markets.

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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226008-175313 + Details
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