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Significant Accounting Policies (Other Operations and Maintenance Expenses and Other Income) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Component Of Other Income And Expense [Line Items] |  |  |  |
Other operations and maintenance expense |  | $ 3,068 | $ 3,243 | $ 2,711
Other income | [1] | 358 | 429 | 312
Dominion Energy Gas Holdings, LLC |  |  |  |
Component Of Other Income And Expense [Line Items] |  |  |  |
Other income |  | 104 | 87 | 63
Scenario, Previously Reported |  |  |  |
Component Of Other Income And Expense [Line Items] |  |  |  |
Other operations and maintenance expense |  | 2,875 | 3,064 | 2,595
Other income |  | 165 | 250 | 16
Scenario, Previously Reported | Dominion Energy Gas Holdings, LLC |  |  |  |
Component Of Other Income And Expense [Line Items] |  |  |  |
Other operations and maintenance expense |  | 440 | 393 | 326
Other income |  | $ 20 | $ 11 | $ 1
[1] | See Note 9 for amounts attributable to related parties.

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- Definition Other operating and maintenance expenses including selling, general and administrative expenses. + References No definition available. + Details
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- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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