Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Derivatives Fair Value [Line Items]
Derivative Asset		$ 294		$ 307
Derivative Liabilities		279		284
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		93		166
Derivative Liabilities		103		66
Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		29		32	[1]
Derivative Liabilities		19		8
Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[2]	223		169
Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		209		163
Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		14		6
Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		63		75
Current Assets | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		60		75
Current Assets | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		3
Current Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	3
Current Assets | Dominion Energy Gas Holdings, LLC | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		3
Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	71		138
Noncurrent Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		41		95
Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		4		11
Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		26		32
Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		30		91
Noncurrent Assets | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		30		91
Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		26	[1]	32
Noncurrent Assets | Dominion Energy Gas Holdings, LLC | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		26		32
Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities	[5]	157		250
Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		129		195
Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		26		53
Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		2
Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		25		53
Current Liabilities | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		15		9
Current Liabilities | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		10		44
Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[6]	11		8
Current Liabilities | Dominion Energy Gas Holdings, LLC | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities				6
Current Liabilities | Dominion Energy Gas Holdings, LLC | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		9
Current Liabilities | Dominion Energy Gas Holdings, LLC | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		2
Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	122		34
Noncurrent Liabilities [Member] | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		6		2
Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		116		32
Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		78		13
Noncurrent Liabilities [Member] | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		78		13
Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	8
Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		8
Fair Value - Derivatives under Hedge Accounting [Member]
Derivatives Fair Value [Line Items]
Derivative Asset		105		54
Derivative Liabilities		166		191
Fair Value - Derivatives under Hedge Accounting [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		3
Derivative Liabilities		88		57
Fair Value - Derivatives under Hedge Accounting [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		29		32	[1]
Derivative Liabilities		19		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[2]	69		11
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		55		5
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		14		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		3
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		3
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	3
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Dominion Energy Gas Holdings, LLC | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		3
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	36		43
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		6
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		4		11
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		26		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		26	[1]	32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Dominion Energy Gas Holdings, LLC | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		26		32
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities	[5]	45		158
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		17		103
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		26		53
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		2
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		10		44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		10		44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[6]	11		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities				6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		9
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		2
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	121		33
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		5		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		116		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		78		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Virginia Electric and Power Company | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		78		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	8
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		8
Derivatives Not Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Derivative Asset		189		253
Derivative Liabilities		113		93
Derivatives Not Designated as Hedging Instruments | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		90		166
Derivative Liabilities		15		9
Derivatives Not Designated as Hedging Instruments | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[2]	154		158
Derivatives Not Designated as Hedging Instruments | Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		154		158
Derivatives Not Designated as Hedging Instruments | Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		60		75
Derivatives Not Designated as Hedging Instruments | Current Assets | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		60		75
Derivatives Not Designated as Hedging Instruments | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	35		95
Derivatives Not Designated as Hedging Instruments | Noncurrent Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		35		95
Derivatives Not Designated as Hedging Instruments | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		30		91
Derivatives Not Designated as Hedging Instruments | Noncurrent Assets | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		30		91
Derivatives Not Designated as Hedging Instruments | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities	[5]	112		92
Derivatives Not Designated as Hedging Instruments | Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		112		92
Derivatives Not Designated as Hedging Instruments | Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		15		9
Derivatives Not Designated as Hedging Instruments | Current Liabilities | Virginia Electric and Power Company | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		15		9
Derivatives Not Designated as Hedging Instruments | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	1		1
Derivatives Not Designated as Hedging Instruments | Noncurrent Liabilities [Member] | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		$ 1		$ 1

[1] Current derivative liabilities are presented in other current liabilities in Virginia Power's Consolidated Balance Sheets.

[2] Current derivative assets are presented in other current assets in Dominion Energy's Consolidated Balance Sheets.

[3] Current derivative assets are presented in other current assets in Virginia Power's Consolidated Balance Sheets.

[4] Noncurrent derivative assets are presented in other deferred charges and other assets in Dominion Energy's Consolidated Balance Sheets.

[5] Current derivative liabilities are presented in other current liabilities in Dominion Energy's Consolidated Balance Sheets.

[6] Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in Virginia Power's Consolidated Balance Sheets.

[7] Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in Dominion Energy's Consolidated Balance Sheets.

[8] Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in Dominion Energy Gas' Consolidated Balance Sheets.