Variable Interest Entities (Narrative) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016 USD ($) generator MW	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Variable Interest Entity [Line Items]
Securities due within one year		$ 1,709	$ 1,825
Amount of long term debt		30,231	23,468
Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Securities due within one year		678	476
Amount of long term debt		9,852	8,892
Dominion Gas Holdings, LLC
Variable Interest Entity [Line Items]
Securities due within one year		0	400
Amount of long term debt		3,528	2,869
Variable Interest Entity, Primary Beneficiary | SBL Holdco
Variable Interest Entity [Line Items]
Securities due within one year		17
Amount of long term debt		$ 377
Variable Interest Entity, Primary Beneficiary | Partnership Interest | Limited Partner | Dominion Midstream Partners, LP
Variable Interest Entity [Line Items]
Percentage of limited partner interests in Dominion Midstream Partners, LP		50.90%
Variable Interest Entity, Primary Beneficiary | Partnership Interest | Preferred Partner | Dominion Midstream Partners, LP
Variable Interest Entity [Line Items]
Percentage of limited partner interests in Dominion Midstream Partners, LP		37.50%
Variable Interest Entity, Primary Beneficiary | Merchant Solar Projects | Partnership Interest
Variable Interest Entity [Line Items]
Initial membership interest percentage	67.00%
Variable Interest Entity, Not Primary Beneficiary | Virginia Electric and Power Company | DRS
Variable Interest Entity [Line Items]
Shared services purchased		$ 346	318	$ 335
Variable Interest Entity, Not Primary Beneficiary | Dominion Gas Holdings, LLC | DRS
Variable Interest Entity [Line Items]
Shared services purchased		$ 123	115	106
Variable Interest Entity, Not Primary Beneficiary | Distribution | Atlantic Coast Pipeline | Pipelines | Jointly Owned Natural Gas Pipeline
Variable Interest Entity [Line Items]
Initial membership interest percentage		48.00%
Potential VIE | Virginia Electric and Power Company
Variable Interest Entity [Line Items]
Number of non utility generators | generator		5
Number of expired non-utility generators | generator		2
Aggregate generation capacity from long-term power and capacity contracts (MW) | MW		418
Remaining purchase commitments		$ 287
Payment for electric capacity		144	200	223
Payment for electric energy		$ 31	$ 83	$ 138