Variable Interest Entities - (Narrative) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) MW Generators	Dec. 31, 2016 USD ($)
Variable Interest Entity, Primary Beneficiary \| Partnership Interest \| Merchant Solar Projects
Initial membership interest percentage	67.00%
Variable Interest Entity, Primary Beneficiary \| Dominion Energy Midstream Partners, LP \| Partnership Interest \| Limited Partner
Percentage of limited partner interests in Dominion Midstream Partners, LP	60.90%
Variable Interest Entity, Primary Beneficiary \| Dominion Energy Midstream Partners, LP \| Partnership Interest \| Preferred Partner
Percentage of limited partner interests in Dominion Midstream Partners, LP	37.50%
Variable Interest Entity, Not Primary Beneficiary \| Distribution \| Atlantic Coast Pipeline \| Pipelines \| Jointly Owned Natural Gas Pipeline
Initial membership interest percentage	48.00%
SBL Holdco \| Variable Interest Entity, Primary Beneficiary
Securities due within one year	$ 31
Long term debt	299
Virginia Electric and Power Company
Securities due within one year	350	$ 850
Long term debt	11,321	10,496
Payables to affiliates	209	125
Virginia Electric and Power Company \| Variable Interest Entity, Not Primary Beneficiary \| DES
Payables to affiliates	107	36
Shared Services Purchased	335	$ 340	$ 346
Virginia Electric and Power Company \| Variable Interest Entity (VIE) or Potential VIE, Information Unavailability
Long term capacity contract non utility generators (generators) \| Generators		3
Number of expired non-utility generators \| Generators		2
Aggregate generation capacity from long-term power and capacity contracts (MW) \| MW		218
Remaining purchase commitments	150
Payment for electric capacity	50	$ 86	144
Payment for electric energy	18	24	31
Dominion Energy Gas Holdings, LLC
Securities due within one year	748	5
Long term debt	7,022	4,295
Payables to affiliates	124	138
Dominion Energy Gas Holdings, LLC \| Dominion Energy Questar Pipeline
Equity Contribution	37
Dominion Energy Gas Holdings, LLC \| Variable Interest Entity, Not Primary Beneficiary \| DES
Payables to affiliates	43	14
Shared Services Purchased	106	106	98
Dominion Energy Gas Holdings, LLC \| Variable Interest Entity, Not Primary Beneficiary \| DECGS And DEQPS
Payables to affiliates	6	6
Shared Services Purchased	$ 45	$ 45	$ 18

This item represents the entity's aggregate generation capacity from long-term power and capacity contracts.

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- Definition

Costs incurred in purchasing electric capacity.

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Equity contribution.

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Long Term Capacity Contract Non Utility Generators.

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Long-term capacity contract expired number of nonutility generators.

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Shared Services Purchased.

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- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

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- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

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