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Employee Benefit Plans (Fair values of pension and post retirement plan assets by asset category) (Parenthetical) (Detail) - Collective Bargaining Agreement - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |
Common stock | $ 508 |
Pension Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pending sales of securities | 52 | $ 12
Net accrued income | 24 | 21
Pending purchases of securities | 99 | 22
Other Postretirement Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pending sales of securities | 2 | 3
Net accrued income | 2 | 5
Pending purchases of securities | 6 | 5
Dominion Energy Gas Holdings, LLC | Pension Benefits |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Pending sales of securities | 2 | 1
Net accrued income | 2 | 2
Pending purchases of securities | $ 5 | $ 2

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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- Details
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