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Employee Benefit Plans (Benefit Obligation in Excess of Plan Assets) (Detail) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Pension Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Benefit obligation | $ 9,552 | $ 7,705
Fair value of plan assets | 7,471 | 5,398
Other Postretirement Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Benefit obligation | 341 | 164
Fair value of plan assets | $ 10 | 136
Other Postretirement Benefits | Dominion Energy Gas Holdings, LLC |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Benefit obligation |  | 134
Fair value of plan assets |  | $ 126

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- Definition Amount of accumulated benefit obligation for defined benefit pension plan with projected benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920 + Details
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- Definition Amount of plan asset for defined benefit pension plan with projected benefit obligation in excess of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2417-114920 + Details
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