Fair Value Measurements (Financial Instruments' Carrying Amounts and Fair Values) (Details) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Valuation of certain fair value hedges		$ 14	$ 7
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[1]	26,287	21,873
Junior subordinated notes	[2]	2,980	1,340
Remarketable subordinated notes	[2]	2,371	2,080
Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[1],[3]	29,077	23,210
Junior subordinated notes	[2],[3]	3,030	1,192
Remarketable subordinated notes	[2],[3]	2,392	2,129
Virginia Electric and Power Company | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[2]	9,642	9,368
Virginia Electric and Power Company | Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[2],[3]	11,259	10,400
Dominion Gas Holdings, LLC | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[4]	3,945	3,269
Dominion Gas Holdings, LLC | Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[3],[4]	$ 4,139	$ 3,299

[1] Carrying amount includes amounts which represent the unamortized debt issuance costs, discount and/or premium, and foreign currency remeasurement adjustments. At September 30, 2016 and December 31, 2015, includes the valuation of certain fair value hedges associated with fixed rate debt of $14 million and $7 million, respectively.

[2] Carrying amount includes amounts which represent the unamortized debt issuance costs, discount and/or premium.

[3] Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issues with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

[4] Carrying amount includes amounts which represent the unamortized debt issuance costs, discount and/or premium, and foreign currency remeasurement adjustments.