Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Amount contributed to Atlantic Coast Pipeline	$ 146	$ 23
Investment in equity method affiliates	1,713		$ 1,561	[1]
Atlantic Coast Pipeline
Gain (Loss) on Investments [Line Items]
Amount contributed to Atlantic Coast Pipeline	117
Dominion Gas Holdings, LLC
Gain (Loss) on Investments [Line Items]
Equity in earnings on investments	7	6
Dominion Gas Holdings, LLC | Iroquois | Partnership Interest
Gain (Loss) on Investments [Line Items]
Equity in earnings on investments	7	6
Distributions received from investment	6	$ 6
Investment in equity method affiliates	99		98
Carrying amount of investment that exceeded share of underlying equity	8		8
Categories of Investments, Marketable Securities, Trading Securities
Gain (Loss) on Investments [Line Items]
Rabbi trust securities	$ 108		$ 104

[1] Dominion’s Consolidated Balance Sheet at December 31, 2016 has been derived from the audited Consolidated Balance Sheet at that date.