Fair Value Measurements (Financial Instruments' Carrying Amounts and Fair Values) (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Valuation of certain fair value hedges associated with fixed rate debt		$ 2	$ (1)
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[1]	28,849	26,587
Junior subordinated notes	[2]	3,980	2,980
Remarketable subordinated notes	[2]	1,376	2,373
Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[1],[3]	31,017	28,273
Junior subordinated notes	[2],[3]	4,086	2,893
Remarketable subordinated notes	[2],[3]	1,409	2,418
Virginia Electric and Power Company | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[2]	11,200	10,530
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]	12,493	11,584
Dominion Energy Gas Holdings, LLC | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[4]	3,553	3,528
Dominion Energy Gas Holdings, LLC | Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	[3],[4]	$ 3,667	$ 3,603

[1] Carrying amount includes amounts which represent the unamortized debt issuance costs, discount or premium, and foreign currency remeasurement adjustments. At June 30, 2017 and December 31, 2016, includes the valuation of certain fair value hedges associated with fixed rate debt of $2 million and $(1) million, respectively.

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