Derivatives and Hedge Accounting Activities (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Derivatives Fair Value [Line Items]
Derivative Asset		$ 244		$ 307
Derivative Liabilities		90		284
Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		129	[1]	166
Derivative Liabilities		23		66
Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Derivative Liabilities		1		8
Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		94	[2]	169	[3]
Current Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[3]	50		75
Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		78		163
Current Assets | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		48		75
Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		16		6
Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		2
Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	150		138
Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		79		91	[1]
Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	44		32
Noncurrent Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		78		95
Noncurrent Assets | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		75		91
Noncurrent Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		28		11
Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		4
Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		49	[6]	250	[7]
Current Liabilities | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[7]	20		53
Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	1		8
Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		29		195
Current Liabilities | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		9		9
Current Liabilities | Commodity | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities				6
Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		19		53
Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		11		44
Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		1		2
Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		1		2
Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	41		34
Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]	3		13
Noncurrent Liabilities [Member] | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		2		2
Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		39		32
Noncurrent Liabilities [Member] | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		3		13
Fair Value - Derivatives under Hedge Accounting [Member]
Derivatives Fair Value [Line Items]
Derivative Asset		106		54
Derivative Liabilities		72		191
Fair Value - Derivatives under Hedge Accounting [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset	[1]	6
Derivative Liabilities		14		57
Fair Value - Derivatives under Hedge Accounting [Member] | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Derivative Liabilities		1		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		33	[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]	2
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		17		5
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate
Derivatives Fair Value [Line Items]
Derivative Asset		16		6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		2
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	73		43
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		4
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset	[5]	44		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Commodity
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		28		11
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		4
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Assets | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Asset		44		32
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		32	[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]	11		44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities	[8]	1		8
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		12		103
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Commodity | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities				6
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		19		53
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Interest rate | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		11		44
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency
Derivatives Fair Value [Line Items]
Derivative Liabilities		1		2
Fair Value - Derivatives under Hedge Accounting [Member] | Current Liabilities | Foreign currency | Dominion Energy Gas Holdings, LLC
Derivatives Fair Value [Line Items]
Derivative Liabilities		1		2
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative Liabilities	[9]	40		33
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities	[10]	3		13
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		1		1
Fair Value - Derivatives under Hedge Accounting [Member] | Noncurrent Liabilities [Member] | Interest rate
Derivatives Fair Value [Line Items]
Derivative Liabilities		39		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		3		13
Fair Value ? Derivatives not under Hedge Accounting
Derivatives Fair Value [Line Items]
Derivative Asset		138		253
Derivative Liabilities		18		93
Fair Value ? Derivatives not under Hedge Accounting | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		123	[1]	166
Derivative Liabilities		9		9
Fair Value ? Derivatives not under Hedge Accounting | Current Assets
Derivatives Fair Value [Line Items]
Derivative Asset		61	[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]	48		75
Fair Value ? Derivatives not under Hedge Accounting | Current Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		61		158
Fair Value ? Derivatives not under Hedge Accounting | Current Assets | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		48		75
Fair Value ? Derivatives not under Hedge Accounting | Noncurrent Assets
Derivatives Fair Value [Line Items]
Derivative Asset	[4]	77		95
Fair Value ? Derivatives not under Hedge Accounting | Noncurrent Assets | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		75		91	[1]
Fair Value ? Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity
Derivatives Fair Value [Line Items]
Derivative Asset		77		95
Fair Value ? Derivatives not under Hedge Accounting | Noncurrent Assets | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Asset		75		91
Fair Value ? Derivatives not under Hedge Accounting | Current Liabilities
Derivatives Fair Value [Line Items]
Derivative Liabilities		17	[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]	9		9
Fair Value ? Derivatives not under Hedge Accounting | Current Liabilities | Commodity
Derivatives Fair Value [Line Items]
Derivative Liabilities		17		92
Fair Value ? Derivatives not under Hedge Accounting | Current Liabilities | Commodity | Virginia Electric and Power Company
Derivatives Fair Value [Line Items]
Derivative Liabilities		9		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
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.