Related-Party Transactions (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Commodity purchases from affiliates	$ 690	$ 930	$ 674
Services provided by affiliates	503	450	453
Virginia Electric and Power Company \| Affiliated Entity
Related Party Transaction [Line Items]
Services provided to related parties	24	24	25
Dominion Energy Gas Holdings, LLC
Related Party Transaction [Line Items]
Services provided to related parties	164	260	190
Commodity purchases from affiliates	249	168	173
Services provided by affiliates	226	169	193
Other receivables	7	13
Other deferred charges and other assets	12
Dominion Energy Gas Holdings, LLC \| Affiliated Entity
Related Party Transaction [Line Items]
Services provided to related parties	12		$ 10
Imbalances receivable from affiliates	8	16
Imbalances payable to affiliates	$ 1	$ 4

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Amount receivable from related parties classified as other.

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Carrying value as of the balance sheet date of obligations incurred and payable to an underproduced working interest owner when an overproduced working interest owner has sold gas in excess of the party's ownership percentage. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of assets classified as other.

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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