Derivatives and Hedge Accounting Activities (Schedule of Offsetting Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	$ 272	$ 379
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	272	379
Total derivatives, not subject to a master netting or similar arrangement	7	9
Gross Amounts of Recognized Assets, Total	279	388
Derivative Asset	279	388
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	67	141
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	205	238
Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	211	217
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	211	217
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	14	37
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	197	180
Commodity \| Exchange
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	44	138
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	44	138
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	44	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	0	56
Interest rate \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	17	24
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	17	24
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	9	22
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	8	2
Virginia Electric and Power Company
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	153	114
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	153	114
Total derivatives, not subject to a master netting or similar arrangement	41	13
Gross Amounts of Recognized Assets, Total	194	127
Derivative Asset	194	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	151	101
Virginia Electric and Power Company \| Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	147	101
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	147	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	145	98
Virginia Electric and Power Company \| Interest rate \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	6	13
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	6	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	6	3
Dominion Gas Holdings, LLC
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	0	11
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	0	11
Derivative Asset		11
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	0	11
Dominion Gas Holdings, LLC \| Commodity \| Over-the-counter
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	0	11
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet	0	11
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	0	0
Net Amounts	$ 0	$ 11

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