Derivatives and Hedge Accounting Activities (Gains and Losses on Derivatives in Cash Flow Hedging Relationships) (Detail) - Cash Flow Hedges - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[1]	$ (144)	$ (36)	$ (278)	$ 68
Amount of Gain (Loss) Reclassified From AOCI to Income		7	(40)	77	(95)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[2]	(190)	48	(405)	141
Virginia Electric and Power Company
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[3]	(21)	4	(45)	13
Amount of Gain (Loss) Reclassified From AOCI to Income				(1)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[4]	(190)	48	(408)	141
Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[5]	(49)	4	(117)	(6)
Amount of Gain (Loss) Reclassified From AOCI to Income		(12)	(7)	(15)	(22)
Commodity
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[1]	(5)	(58)	96	(1)
Amount of Gain (Loss) Reclassified From AOCI to Income		33	(26)	128	(49)
Commodity | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[5]	1	(5)	3	(11)
Amount of Gain (Loss) Reclassified From AOCI to Income		2	(3)	4	(8)
Commodity | Operating Revenue
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		35	(26)	127	(55)
Commodity | Operating Revenue | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		2	(3)	4	(8)
Commodity | Purchased Gas
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income		(2)		1	(2)
Commodity | Electric Fuel and Other Energy-Related Purchases
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Reclassified From AOCI to Income					8
Interest rate
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[1],[6]	(124)	23	(350)	70
Amount of Gain (Loss) Reclassified From AOCI to Income	[6]	(14)	(12)	(37)	(36)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[2],[6]	(190)	48	(405)	141
Interest rate | Virginia Electric and Power Company
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[3],[7]	(21)	4	(45)	13
Amount of Gain (Loss) Reclassified From AOCI to Income	[7]			(1)
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[4],[7]	(190)	48	(408)	141
Interest rate | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[5],[8]	(36)	10	(96)	6
Amount of Gain (Loss) Reclassified From AOCI to Income	[8]	(2)	(2)	(5)	(4)
Foreign currency
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[1],[9]	(15)	(1)	(24)	(1)
Amount of Gain (Loss) Reclassified From AOCI to Income	[9]	(12)	(2)	(14)	(10)
Foreign currency | Dominion Energy Gas Holdings, LLC
Derivative Instruments Gain Loss [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives	[5],[10]	(14)	(1)	(24)	(1)
Amount of Gain (Loss) Reclassified From AOCI to Income	[10]	$ (12)	$ (2)	$ (14)	$ (10)

[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 deferred into AOCI have no associated effect in Dominion Energy Gas’ Consolidated Statements of Income.

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

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

[8] Amounts recorded in Dominion Energy Gas’ Consolidated Statements of Income are classified in interest and related charges

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

[10] Amounts recorded in Dominion Energy Gas’ Consolidated Statements of Income are classified in other income.