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Employee Benefit Plans (AOCI and regulatory assets and liabilities that have not been recognized as components of periodic benefit (credit) cost) (Parenthetical) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | [1] | $ 3,189 | $ 3,204
Amount included in AOCI |  | 1,900 | 1,900
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | [1] | (157) | (136)
Amount included in AOCI |  | (87) | (103)
Dominion Energy Gas Holdings, LLC | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | [2] | 367 | 458
Amount included in AOCI |  | 134 | 167
Dominion Energy Gas Holdings, LLC | Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total | [2] | $ 24 | $ 67
[1] | As of December 31, 2017, of the $3.2 billion and $(157) million related to pension benefits and other postretirement benefits, $1.9 billion and $(87) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities. As of December 31, 2016, of the $3.2 billion and $(136) million related to pension benefits and other postretirement benefits, $1.9 billion and $(103) million, respectively, are included in AOCI, with the remainder included in regulatory assets and liabilities.
[2] | As of December 31, 2017, of the $367 million related to pension benefits, $134 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $24 million related to other postretirement benefits is included entirely in regulatory assets and liabilities. As of December 31, 2016, of the $458 million related to pension benefits, $167 million is included in AOCI, with the remainder included in regulatory assets and liabilities; the $67 million related to other postretirement benefits is included entirely in regulatory assets and liabilities.

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