Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Derivatives Fair Value [Line Items]
Derivative Asset		$ 250		$ 307
Derivative Liabilities		118		284
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		147	[1]	166
Derivative Liabilities		14		66
Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		34		32
Derivative Liabilities		16		8
Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		89	[2]	169	[3]
Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	57		75
Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		77		163
Current Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		49		75
Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		12		6
Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		8
Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	161		138
Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		90		91	[1]
Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	34		32
Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		82		95
Noncurrent Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		77		91
Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		46		11
Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		13
Noncurrent Assets | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		1
Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		33		32
Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		33		32
Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		69	[6]	250	[7]
Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	12		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		52		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		7		6
Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		12		53
Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		4		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		5		2
Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		5		2
Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	49		34
Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]	2		13
Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[11]	3
Noncurrent Liabilities [Member] | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		2
Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		46		32
Noncurrent Liabilities [Member] | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		13
Noncurrent Liabilities [Member] | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		3
Fair Value - Derivatives under Hedge Accounting [Member]
Derivatives Fair Value [Line Items]
Derivative Asset		102		54
Derivative Liabilities		95		191
Fair Value - Derivatives under Hedge Accounting [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[1]	21
Derivative Liabilities		6		57
Fair Value - Derivatives under Hedge Accounting [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		34		32
Derivative Liabilities		16		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		22	[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]	8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		10		5
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		12		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		8
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	80		43
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	34		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		46		11
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		33		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		33		32
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		47	[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]	4		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		30		103
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity contracts | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		7		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		12		53
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		4		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		5		2
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		5		2
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	48		33
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]	2		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[11]	3
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		46		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		2		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		3
Fair Value - Derivatives not under Hedge Accounting
Derivatives Fair Value [Line Items]
Derivative Asset		148		253
Derivative Liabilities		23		93
Fair Value - Derivatives not under Hedge Accounting | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		126	[1]	166
Derivative Liabilities		8		9
Fair Value - Derivatives not under Hedge Accounting | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		67	[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]	49		75
Fair Value - Derivatives not under Hedge Accounting | Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		67		158
Fair Value - Derivatives not under Hedge Accounting | Current Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		49		75
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	81		95
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		77		91	[1]
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Derivative Asset		81		95
Fair Value - Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity contracts | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		77		91
Fair Value - Derivatives not under Hedge Accounting | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		22	[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		22		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.

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