Related-Party Transactions (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Derivative Asset		$ 295,000,000		$ 295,000,000		$ 388,000,000
Derivative Liabilities		422,000,000		422,000,000		343,000,000
Capital expenditures				4,536,000,000	$ 3,632,000,000
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Derivative Asset		118,000,000		118,000,000		127,000,000
Derivative Liabilities		291,000,000		291,000,000		86,000,000
Commodity purchases from affiliates		172,000,000	$ 123,000,000	416,000,000	469,000,000
Services provided by affiliates	[1]	105,000,000	96,000,000	347,000,000	313,000,000
Services provided to affiliates		5,000,000	5,000,000	17,000,000	15,000,000
Capital expenditures				1,835,000,000	1,840,000,000
Outstanding borrowings, net of repayments, under money pool for non-regulated subsidiaries		0		0		0
Virginia Electric and Power Company | Affiliate
Related Party Transaction [Line Items]
Derivative Asset		28,000,000		28,000,000		13,000,000
Derivative Liabilities		15,000,000		15,000,000		22,000,000
Virginia Electric and Power Company | Affiliate | Services provided by affiliates
Related Party Transaction [Line Items]
Capital expenditures		32,000,000	32,000,000	109,000,000	105,000,000
Virginia Electric and Power Company | Principal Owner
Related Party Transaction [Line Items]
Short term demand note		0		0		376,000,000
Virginia Electric and Power Company | Other deferred credits and other liabilities
Related Party Transaction [Line Items]
Amounts due to Dominion		376,000,000		376,000,000		316,000,000
Virginia Electric and Power Company | Other deferred charges and other assets
Related Party Transaction [Line Items]
Amounts due from Dominion		111,000,000		111,000,000		77,000,000
Dominion Gas Holdings, LLC
Related Party Transaction [Line Items]
Derivative Asset		14,000,000		14,000,000		11,000,000
Derivative Liabilities		6,000,000		6,000,000		14,000,000
Amounts due from Dominion	[2]	1,000,000		1,000,000		1,000,000
Commodity purchases from affiliates		2,000,000	3,000,000	7,000,000	7,000,000
Services provided by affiliates	[3]	34,000,000	30,000,000	94,000,000	75,000,000
Services provided to affiliates		16,000,000	17,000,000	51,000,000	52,000,000
Capital expenditures				610,000,000	514,000,000
Other receivables	[4]	9,000,000		9,000,000		7,000,000
Customer receivables from related parties		1,000,000		1,000,000		4,000,000
Affiliated notes receivable	[5]	17,000,000		17,000,000		14,000,000
Dominion Gas Holdings, LLC | Revolving Credit Facility | IRCA
Related Party Transaction [Line Items]
Borrowings under IRCA						95,000,000
Dominion Gas Holdings, LLC | Services provided by affiliates
Related Party Transaction [Line Items]
Commodity purchases from affiliates	[6]	36,000,000	30,000,000	108,000,000	99,000,000
Dominion Gas Holdings, LLC | Affiliate | Services provided by affiliates
Related Party Transaction [Line Items]
Capital expenditures		13,000,000	$ 16,000,000	37,000,000	$ 40,000,000
Dominion Gas Holdings, LLC | Noncurrent Pension and Other Postretirement Benefit Assets
Related Party Transaction [Line Items]
Amounts due from Dominion, noncurrent		$ 686,000,000		$ 686,000,000		$ 652,000,000

[1] Includes capitalized expenditures of $32 million for both the three months ended September 30, 2016 and 2015, and $109 million and $105 million for the nine months ended September 30, 2016 and 2015, respectively.

[2] Amounts are presented in other current assets in Dominion Gas' Consolidated Balance Sheets.

[3] Amounts primarily attributable to Atlantic Coast Pipeline.

[4] Represents amounts due from Atlantic Coast Pipeline, a related-party VIE.

[5] Amounts are presented in other deferred charges and other assets in Dominion Gas' Consolidated Balance Sheets.

[6] Includes capitalized expenditures of $13 million and $16 million for the three months ended September 30, 2016 and 2015, respectively, and $37 million and $40 million for the nine months ended September 30, 2016 and 2015