Derivatives and Hedge Accounting Activities (Schedule of Offsetting Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 417	$ 335
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	417	335
Total derivatives, not subject to a master netting or similar arrangement	5	8
Gross Amounts of Recognized Liabilities, Total	422	343
Derivative Liabilities	422	343
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	97	141
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	320	194
Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	43	70
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	43	70
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	20	37
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	23	33
Commodity | Exchange
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	63	82
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	63	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	63	82
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	0	0
Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	307	183
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	307	183
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	10	22
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	297	161
Foreign currency | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	4	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	4	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	0	0
Net Amounts	0	0
Virginia Electric and Power Company
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	276	64
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	276	64
Total derivatives, not subject to a master netting or similar arrangement	15	22
Gross Amounts of Recognized Liabilities, Total	291	86
Derivative Liabilities	291	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	0	0
Net Amounts	274	51
Virginia Electric and Power Company | Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	9	5
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	9	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	0	0
Net Amounts	7	2
Virginia Electric and Power Company | Interest rate | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	267	59
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	267	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	0	0
Net Amounts	267	49
Dominion Gas Holdings, LLC
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	6	14
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	6	14
Derivative Liabilities	6	14
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	5	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	1	14
Dominion Gas Holdings, LLC | Commodity | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	2	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	2	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	1	0
Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral	0	0
Net Amounts	1	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	0	0
Net Amounts	0	14
Dominion Gas Holdings, LLC | Foreign currency | Over-the-counter
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	4	0
Gross Amounts Offset in the Consolidated Balance Sheet	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	4	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	0	0
Net Amounts	$ 0	$ 0