Derivatives and Hedge Accounting Activities (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	$ 288	$ 379
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	288	379
Total derivatives, not subject to a master netting or similar arrangement	7	9
Gross Amounts of Recognized Assets, Total	295	388
Derivative Asset	295	388
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	97	141
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	191	238
Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	173	217
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	173	217
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	20	37
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	153	180
Commodity \| Exchange
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	88	138
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	88	138
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	63	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	25	56
Interest rate \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	19	24
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	19	24
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	10	22
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	9	2
Foreign currency \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	8	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	8	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	4	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	4	0
Virginia Electric and Power Company
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	90	114
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	90	114
Total derivatives, not subject to a master netting or similar arrangement	28	13
Gross Amounts of Recognized Assets, Total	118	127
Derivative Asset	118	127
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	2	13
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	88	101
Virginia Electric and Power Company \| Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	88	101
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	88	101
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	2	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	86	98
Virginia Electric and Power Company \| Interest rate \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	2	13
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	2	13
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	10
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	2	3
Dominion Gas Holdings, LLC
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	14	11
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	14	11
Derivative Asset	14	11
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	5	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	9	11
Dominion Gas Holdings, LLC \| Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	6	11
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	6	11
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	1	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	5	11
Dominion Gas Holdings, LLC \| Foreign currency \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	8	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	8	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	4	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	$ 4	$ 0

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