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Asset Retirement Obligations (Changes to AROs) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |  |  |  |
AROs, Beginning balance |  | $ 2,485 | [1] | $ 2,103 |
Obligations incurred during the period |  | 37 |  | 204 | [2]
Obligations settled during the period |  | (214) |  | (171) |
Revisions in estimated cash flows |  | 7 |  | 245 | [3]
Accretion |  | 117 |  | 104 |
AROs, Ending balance | [1] | 2,432 |  | 2,485 |
Asset retirement obligations, non current |  | 2,169 |  | 2,236 |
Current Liabilities |  |  |  |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |  |  |  |
Asset retirement obligation, current |  | 263 |  | 249 |
Virginia Electric and Power Company |  |  |  |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |  |  |  |
AROs, Beginning balance |  | 1,443 |  | 1,247 |
Obligations incurred during the period |  | 11 |  | 9 |
Obligations settled during the period |  | (152) |  | (115) |
Revisions in estimated cash flows |  | (1) |  | 245 | [3]
Accretion |  | 64 |  | 57 |
AROs, Ending balance |  | 1,365 |  | 1,443 |
Asset retirement obligation, current |  | 216 |  | 181 |
Asset retirement obligations, non current |  | 1,149 |  | 1,262 |
Dominion Energy Gas Holdings, LLC |  |  |  |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |  |  |  |
AROs, Beginning balance |  | 156 | [4] | 149 |
Obligations incurred during the period |  | 2 |  | 6 |
Obligations settled during the period |  | (7) |  | (8) |
Accretion |  | 9 |  | 9 |
AROs, Ending balance | [4] | 160 |  | 156 |
Dominion Energy Gas Holdings, LLC | Other Deferred Credits And Other Liabilities |  |  |  |  |
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] |  |  |  |  |
Asset retirement obligations, non current |  | $ 146 |  | $ 147 |
[1] | Includes $249 million and $263 million reported in other current liabilities at December 31, 2016, and 2017, respectively.
[2] | Primarily reflects AROs assumed in the Dominion Energy Questar Combination. See Note 3 for further information.
[3] | Primarily reflects future ash pond and landfill closure costs at certain utility generation facilities. See Note 22 for further information.
[4] | Includes $147 million and $146 million reported in other deferred credits and other liabilities, with the remainder recorded in other current liabilities, at December 31, 2016 and 2017, respectively.

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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
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- Definition Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 35 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846 + Details
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- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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