Investments (Equity and Fixed Income Securities, Insurance Contracts and Cash Equivalents in Decommissioning Trust Funds) (Detail) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2019	Dec. 31, 2018		Mar. 31, 2019
Investment Holdings [Line Items]
Fixed income securities Fair Value		$ 1,675
Amortized Cost, Total		3,603	$ 3,348
Total Unrealized Gains		2,188	1,662
Total Unrealized Losses	[1]	(24)	(72)
Fair Value, Total		5,767	4,938	[2]
Fair value of securities in an unrealized loss position		208	833
Net assets related to pending sales and purchases of securities		3
Virginia Electric and Power Company
Investment Holdings [Line Items]
Fixed income securities Fair Value		821
Amortized Cost, Total		1,682	1,643
Total Unrealized Gains		1,012	760
Total Unrealized Losses	[3]	(12)	(34)
Fair Value, Total		2,682	2,369	[4]
Fair value of securities in an unrealized loss position		97	404
Net assets related to pending sales and purchases of securities		3	6
Fixed Income
Investment Holdings [Line Items]
Cash equivalents and other Amortized Cost	[5]	11	4
Cash equivalents and other Fair Value	[5]	11	4
Insurance Contracts
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total		206
Fixed income securities Fair Value		206
Cash Equivalents and Other [Member] | Virginia Electric and Power Company
Investment Holdings [Line Items]
Cash equivalents and other Amortized Cost	[6]	3	6
Cash equivalents and other Fair Value	[6]	3	6
Common/collective trust funds | Fixed Income
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]	63	76
Fixed income securities Fair Value	[7]	63	76
Common/collective trust funds | Fixed Income | Virginia Electric and Power Company
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]		51		$ 47
Fixed income securities Fair Value	[7]		51		47
Corporate debt instruments | Fixed Income
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]	474	435
Fixed income securities Total Unrealized Gains	[7]	27	5
Fixed income securities Total Unrealized Losses	[7]	(1)	(9)
Fixed income securities Fair Value	[7]	500	431
Corporate debt instruments | Fixed Income | Virginia Electric and Power Company
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]		224		244
Fixed income securities Total Unrealized Gains	[7]	13	2
Fixed income securities Total Unrealized Losses	[7]		(5)
Fixed income securities Fair Value	[7]		221		257
Government Securities | Fixed Income
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]	1,073	1,092
Fixed income securities Total Unrealized Gains	[7]	41	17
Fixed income securities Total Unrealized Losses	[7]	(2)	(12)
Fixed income securities Fair Value	[7]	1,112	1,097
Government Securities | Fixed Income | Virginia Electric and Power Company
Investment Holdings [Line Items]
Fixed income securities Amortized Cost, Total	[7]		504		500
Fixed income securities Total Unrealized Gains	[7]	18	7
Fixed income securities Total Unrealized Losses	[7]	(1)	(5)
Fixed income securities Fair Value	[7]		506		$ 517
Equity securities: | U.S.
Investment Holdings [Line Items]
Equity securities Amortized Cost	[8]	1,776	1,741
Equity securities Total Unrealized Gains	[8]	2,120	1,640
Equity securities Total Unrealized Losses	[8]	(21)	(51)
Equity securities Fair Value	[8]	3,875	3,330
Equity securities: | U.S. | Virginia Electric and Power Company
Investment Holdings [Line Items]
Equity securities Amortized Cost	[8]	888	858
Equity securities Total Unrealized Gains	[8]	981	751
Equity securities Total Unrealized Losses	[8]	(11)	(24)
Equity securities Fair Value	[8]	$ 1,858	$ 1,585

[1] The fair value of securities in an unrealized loss position was $208 million and $833 million at June 30, 2019 and December 31, 2018, respectively.

[2] Dominion Energy’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

[3] The fair value of securities in an unrealized loss position was $97 million and $404 million at June 30, 2019 and December 31, 2018, respectively.

[4] Virginia Power’s Consolidated Balance Sheet at December 31, 2018 has been derived from the audited Consolidated Balance Sheet at that date.

[5] Includes pending sales of securities of $3 million at June 30, 2019

[6] Includes pending sales of securities of $3 million and $6 million at June 30, 2019 and December 31, 2018, respectively.

[7] Unrealized gains and losses on fixed income securities are included in AOCI and the nuclear decommissioning trust regulatory liability.

[8] Unrealized gains and losses on equity securities are included in other income and the nuclear decommissioning trust regulatory liability.