Derivatives and Hedge Accounting Activities (Gains and Losses on Derivatives in Cash Flow Hedging Relationships) (Detail) - Cash Flow Hedges - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[1]	$ 40		$ 11	$ 92
Amount of Gain (Loss) Reclassified From AOCI to Income		(137)		47	259
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[2]	39		(58)	(26)
Virginia Electric and Power Company
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[3]	2		(8)	(3)
Amount of Gain (Loss) Reclassified From AOCI to Income		(1)		(1)	(1)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[4]	39		(58)	(26)
Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		(23)		8	(26)
Amount of Gain (Loss) Reclassified From AOCI to Income		(27)		7	(15)
Commodity
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[1]	64		1	164
Amount of Gain (Loss) Reclassified From AOCI to Income		(76)		79	307
Commodity | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		1		(10)	(12)
Amount of Gain (Loss) Reclassified From AOCI to Income		(8)		(8)	4
Commodity | Operating Revenue
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		(90)		81	330
Commodity | Operating Revenue | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		(8)		(8)	4
Commodity | Electric fuel and other energy-related purchases
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		14			(10)
Commodity | Purchased Gas
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income				(2)	(13)
Interest rate
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[1],[5]	(18)	[6]	(8)	(66)
Amount of Gain (Loss) Reclassified From AOCI to Income	[5]	(48)	[6]	(52)	(31)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[2],[5]	39	[6]	(58)	(26)
Interest rate | Virginia Electric and Power Company
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[3],[7]	2		(8)	(3)
Amount of Gain (Loss) Reclassified From AOCI to Income	[7]	(1)		(1)	(1)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[4],[7]	39		(58)	(26)
Interest rate | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		(18)			(8)
Amount of Gain (Loss) Reclassified From AOCI to Income		(6)		(5)	(2)
Foreign currency
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	[1],[8]	(6)		18	(6)
Amount of Gain (Loss) Reclassified From AOCI to Income	[8]	(13)		20	(17)
Foreign currency | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)		(6)		18	(6)
Amount of Gain (Loss) Reclassified From AOCI to Income		$ (13)		$ 20	$ (17)

[1] Amounts deferred into AOCI have no associated effect in Dominion Energy's Consolidated Statements of Income.

[2] Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in Dominion Energy's Consolidated Statements of Income.

[3] Amounts deferred into AOCI have no associated effect in Virginia Power's Consolidated Statements of Income.

[4] Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in Virginia Power's Consolidated Statements of Income.

[5] Amounts recorded in Dominion Energy's Consolidated Statements of Income are classified in interest and related charges.

[6] See Note 9 for amounts attributable to related parties.

[7] Amounts recorded in Virginia Power's Consolidated Statements of Income are classified in interest and related charges.

[8] Amounts recorded in Dominion Energy's Consolidated Statements of Income are classified in other income.