Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Sep. 30, 2018		Dec. 31, 2017
Derivatives Fair Value [Line Items]
Derivative Asset		$ 297		$ 307
Derivative Liabilities		145		284
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		170	[1]	166
Derivative Liabilities		8		66
Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		40		32
Derivative Liabilities		13		8
Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		152	[2]	169	[3]
Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	88		75
Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		94		163
Current Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		60		75
Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		58		6
Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		28
Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	145		138
Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		82		91	[1]
Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	40		32
Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		54		95
Noncurrent Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		45		91
Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		59		11
Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		37
Noncurrent Assets | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		8
Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		32		32
Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		32		32
Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		109	[6]	250	[7]
Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	8		53
Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	13		8
Current Liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		96		195
Current Liabilities | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		8		9
Current Liabilities | Commodity contracts | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		9		6
Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		10		53
Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities				44
Current Liabilities | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		1
Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		2
Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		2
Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	36		34
Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]			13
Noncurrent Liabilities [Member] | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		4		2
Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		32		32
Noncurrent Liabilities [Member] | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities				13
Fair Value - Derivatives under Hedge Accounting [Member]
Derivatives Fair Value [Line Items]
Derivative Asset		160		54
Derivative Liabilities		112		191
Fair Value - Derivatives under Hedge Accounting [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[1]	65
Derivative Liabilities				57
Fair Value - Derivatives under Hedge Accounting [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		40		32
Derivative Liabilities		13		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		66	[2]	11	[3]
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	28
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		8		5
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		58		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		28
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	94		43
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		37
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	40		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		3
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		59		11
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		37
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		8
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		32		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		32		32
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		77	[6]	158	[7]
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]			44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	13		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		64		103
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity contracts | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		9		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		10		53
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities				44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		1
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		2
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		2
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	35		33
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]			13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		32		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities				13
Fair Value - Derivatives not under Hedge Accounting
Derivatives Fair Value [Line Items]
Derivative Asset		137		253
Derivative Liabilities		33		93
Fair Value - Derivatives not under Hedge Accounting | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		105	[1]	166
Derivative Liabilities		8		9
Fair Value - Derivatives not under Hedge Accounting | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		86	[2]	158	[3]
Fair Value - Derivatives not under Hedge Accounting | Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	60		75
Fair Value - Derivatives not under Hedge Accounting | Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		86		158
Fair Value - Derivatives not under Hedge Accounting | Current Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		60		75
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	51		95
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		45		91	[1]
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		51		95
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		45		91
Fair Value - Derivatives not under Hedge Accounting | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		32	[6]	92	[7]
Fair Value - Derivatives not under Hedge Accounting | Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	8		9
Fair Value - Derivatives not under Hedge Accounting | Current Liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		32		92
Fair Value - Derivatives not under Hedge Accounting | Current Liabilities | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		8		9
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	1		1
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Liabilities [Member] | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		$ 1		$ 1

[1] Noncurrent derivative assets are presented in other deferred charges and other assets 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] Noncurrent derivatives assets are presented in other deferred charges and other assets in Dominion Energy Gas’ Consolidated Balance Sheets.

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

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

[8] Current derivative liabilities are presented in other current liabilities in Dominion Energy Gas’ Consolidated Balance Sheets.

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

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