Investments (Narrative) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Contributions to equity method affiliates		$ 87	$ 146
Operating Revenue	[1]	3,466	3,384
Other receivables	[1]	136		$ 126	[2]
Liabilities, other deferred credits and other liabilities		16,853		16,631	[2]
Investment in equity method affiliates		1,638		1,544	[2]
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Operating Revenue	[3]	526	490
Other receivables	[3]	22		15	[4]
Liabilities, other deferred credits and other liabilities		2,904		2,866	[4]
Equity in earnings on investments		9	7
Dominion Energy Gas Holdings, LLC | Partnership Interest
Schedule of Equity Method Investments [Line Items]
Equity in earnings on investments		9	7
Distributions received from investment		7	6
Investment in equity method affiliates		97		95
Carrying amount of investment that exceeded share of underlying equity		8
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Contributions to equity method affiliates		78	117
Atlantic Coast Pipeline | DETI
Schedule of Equity Method Investments [Line Items]
Operating Revenue		46	31
Other receivables		17	$ 12
NedPower Mount Storm LLC
Schedule of Equity Method Investments [Line Items]
Liabilities, other deferred credits and other liabilities		9		17
Trading Securities
Schedule of Equity Method Investments [Line Items]
Rabbi trust securities		$ 114		$ 112

[1] See Note 10 for amounts attributable to related parties.

[2] Dominion Energy’s Consolidated Balance Sheet at December 31, 2017 has been derived from the audited Consolidated Balance Sheet at that date.

[3] See Note 18 for amounts attributable to related parties.

[4] Dominion Energy Gas’ Consolidated Balance Sheet at December 31, 2017 has been derived from the audited Consolidated Balance Sheet at that date.