Derivatives and Hedge Accounting Activities (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 153	$ 335
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	153	335
Total derivatives, not subject to a master netting or similar arrangement	2	8
Gross Amounts of Recognized Liabilities, Total	155	343
Derivative liabilities	155	343
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	67	141
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	27	0
Net Amounts	59	194
Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	23	70
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	23	70
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	14	37
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	9	33
Commodity | Exchange
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	71	82
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	71	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	44	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	27	0
Net Amounts	0	0
Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	53	183
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	53	183
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	9	22
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	44	161
Foreign currency | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	6	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	6	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	6	0
Virginia Electric and Power Company
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	23	64
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	23	64
Total derivatives, not subject to a master netting or similar arrangement	8	22
Gross Amounts of Recognized Liabilities, Total	31	86
Derivative liabilities	31	86
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	2	13
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	21	51
Virginia Electric and Power Company | Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	2	5
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	2	5
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	2	3
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	0	2
Virginia Electric and Power Company | Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	21	59
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	21	59
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	10
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	21	49
Dominion Gas Holdings, LLC
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	11	14
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	11	14
Derivative liabilities	11	14
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	11	14
Dominion Gas Holdings, LLC | Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	5	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	5	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	5	0
Dominion Gas Holdings, LLC | Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	0	14
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	0	14
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	0	14
Dominion Gas Holdings, LLC | Foreign currency | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	6	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	6	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Paid	0	0
Net Amounts	$ 6	$ 0