Operating Segments (Schedule of Segment Reporting Information, by Segment) (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating revenue		$ 3,361.0	$ 3,451.0	$ 3,088.0	$ 3,466.0	$ 3,210.0	$ 3,179.0	$ 2,813.0	$ 3,384.0	$ 13,366.0	[1]	$ 12,586.0	[1]	$ 11,737.0	[1]
Depreciation and amortization										2,000.0		1,905.0		1,559.0
Impairment of assets and related charges										403.0		15.0		4.0
Gains on sales of assets										(380.0)		(147.0)		(40.0)
Equity in earnings of equity method investees										197.0		(18.0)		111.0
Interest income										84.0		82.0		66.0
Interest and related charges										1,493.0		1,205.0		1,010.0
Income tax expense (benefit)										580.0		(30.0)		655.0
Net income		641.0	854.0	449.0	503.0	1,312.0	665.0	390.0	632.0	2,447.0		2,999.0		2,123.0
Investment in equity method investees		1,278.0				1,544.0				1,278.0		1,544.0
Capital expenditures										4,405.0		5,909.0		6,125.0
Capital expenditures										4,254.0		5,504.0		6,085.0
Total assets		77,914.0				76,585.0				77,914.0		76,585.0
Total assets		77,914.0				76,585.0				77,914.0		76,585.0
Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
Operating revenue		532.0	423.0	459.0	526.0	501.0	401.0	422.0	490.0	1,940.0	[2]	1,814.0	[2]	1,638.0	[2]
Depreciation and amortization										244.0		227.0		204.0
Impairment of assets and related charges		219.0								346.0		16.0
Gains on sales of assets										(119.0)		(70.0)		(45.0)
Equity in earnings of equity method investees										24.0		21.0		21.0
Interest income										2.0		2.0		1.0
Interest and related charges	[2]									105.0		97.0		94.0
Income tax expense (benefit)										86.0		51.0		215.0
Net income		(16.0)	136.0	15.0	166.0	313.0	117.0	77.0	108.0	301.0		615.0		392.0
Investment in equity method investees		91.0				95.0				91.0		95.0
Capital expenditures										772.0		778.0		854.0
Total assets		12,351.0				11,940.0				12,351.0		11,940.0
Total assets		12,351.0				11,940.0				12,351.0		11,940.0
Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Operating revenue		1,810.0	2,232.0	1,829.0	1,748.0	1,824.0	2,154.0	1,747.0	1,831.0	7,619.0	[3]	7,556.0	[3]	7,588.0	[3]
Depreciation and amortization										1,132.0		1,141.0		1,025.0
Interest income										10.0		19.0
Interest and related charges	[3]									511.0		494.0		461.0
Income tax expense (benefit)										300.0		774.0		727.0
Net income		239.0	$ 520.0	$ 339.0	$ 184.0	407.0	$ 459.0	$ 318.0	$ 356.0	1,282.0		1,540.0		1,218.0
Capital expenditures										2,542.0		2,729.0		2,649.0
Capital expenditures										2,228.0		2,496.0		2,489.0
Total assets		36,880.0				35,139.0				36,880.0		35,139.0
Total assets		36,880.0				35,139.0				36,880.0		35,139.0
Gas Infrastructure
Segment Reporting Information [Line Items]
Operating revenue										4,221.0		2,832.0		2,069.0
Gas Infrastructure | Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
Operating revenue										1,940.0		1,814.0		1,638.0
Depreciation and amortization										244.0		227.0		214.0
Impairment of assets and related charges										5.0		15.0
Gains on sales of assets										(119.0)		(70.0)		(45.0)
Equity in earnings of equity method investees										24.0		21.0		21.0
Interest income										2.0		2.0		1.0
Interest and related charges										104.0		97.0		92.0
Income tax expense (benefit)										188.0		256.0		237.0
Net income										552.0		436.0		395.0
Investment in equity method investees		91.0				95.0				91.0		95.0
Capital expenditures										772.0		778.0		854.0
Total assets		11,800.0				11,300.0				11,800.0		11,300.0
Total assets		11,800.0				11,300.0				11,800.0		11,300.0
Corporate and Other
Segment Reporting Information [Line Items]
Operating revenue										(208.0)		16.0		(7.0)
Corporate and Other | Dominion Energy Gas Holdings, LLC
Segment Reporting Information [Line Items]
Depreciation and amortization														(10.0)
Impairment of assets and related charges										341.0		1.0
Interest and related charges										1.0				2.0
Income tax expense (benefit)										(102.0)		(205.0)		(22.0)
Net income										(251.0)		179.0		(3.0)
Total assets		600.0				600.0				600.0		600.0
Total assets		600.0				600.0				600.0		600.0
Power Delivery
Segment Reporting Information [Line Items]
Operating revenue										2,206.0		2,206.0		2,210.0
Power Generation
Segment Reporting Information [Line Items]
Operating revenue										7,104.0		6,676.0		6,747.0
Adjustments & Eliminations
Segment Reporting Information [Line Items]
Operating revenue										43.0		856.0		718.0
Adjustments & Eliminations | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Interest income										(4.0)		(3.0)
Interest and related charges										(4.0)		(3.0)		(2.0)
Total assets		(0.1)				(0.1)				(0.1)		(0.1)
Total assets		(0.1)				(0.1)				(0.1)		(0.1)
Intersegment revenue
Segment Reporting Information [Line Items]
Operating revenue										(735.0)		(1,476.0)		(1,339.0)
Intersegment revenue | Gas Infrastructure
Segment Reporting Information [Line Items]
Operating revenue										27.0		834.0		697.0
Intersegment revenue | Corporate and Other
Segment Reporting Information [Line Items]
Operating revenue										674.0		610.0		609.0
Intersegment revenue | Power Delivery
Segment Reporting Information [Line Items]
Operating revenue										23.0		22.0		23.0
Intersegment revenue | Power Generation
Segment Reporting Information [Line Items]
Operating revenue										11.0		10.0		10.0
Eliminations
Segment Reporting Information [Line Items]
Operating revenue										(692.0)		(620.0)		(621.0)
Operating Segments
Segment Reporting Information [Line Items]
Operating revenue										13,366.0		12,586.0		11,737.0
Operating Segments | Gas Infrastructure
Segment Reporting Information [Line Items]
Operating revenue										4,248.0		3,666.0		2,766.0
Depreciation and amortization										615.0		522.0		330.0
Impairment of assets and related charges										8.0
Gains on sales of assets										(186.0)		(147.0)		(44.0)
Equity in earnings of equity method investees										178.0		159.0		105.0
Interest income										64.0		45.0		34.0
Interest and related charges										268.0		109.0		38.0
Income tax expense (benefit)										330.0		487.0		431.0
Net income										1,214.0		898.0		726.0
Investment in equity method investees		1,159.0				1,422.0				1,159.0		1,422.0
Capital expenditures										1,415.0		2,149.0		2,322.0
Total assets		31,500.0				28,000.0				31,500.0		28,000.0
Total assets		31,500.0				28,000.0				31,500.0		28,000.0
Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Operating revenue										466.0		626.0		602.0
Depreciation and amortization										14.0		43.0		30.0
Impairment of assets and related charges										394.0		15.0		4.0
Gains on sales of assets										(200.0)
Equity in earnings of equity method investees										1.0		4.0		22.0
Interest income										126.0		96.0		36.0
Interest and related charges										782.0		644.0		516.0
Income tax expense (benefit)										(204.0)		(1,224.0)		(363.0)
Net income										(608.0)		389.0		(484.0)
Investment in equity method investees		37.0				41.0				37.0		41.0
Capital expenditures										105.0		52.0		43.0
Total assets		11,200.0				12,000.0				11,200.0		12,000.0
Total assets		11,200.0				12,000.0				11,200.0		12,000.0
Operating Segments | Corporate and Other | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Operating revenue										(215.0)				(19.0)
Depreciation and amortization										(25.0)
Interest income										5.0		3.0
Income tax expense (benefit)										(78.0)		(94.0)		(104.0)
Net income										(312.0)		74.0		(173.0)
Operating Segments | Power Delivery
Segment Reporting Information [Line Items]
Operating revenue										2,229.0		2,228.0		2,233.0
Depreciation and amortization										625.0		593.0		537.0
Interest income												4.0
Interest and related charges										265.0		265.0		244.0
Income tax expense (benefit)										160.0		334.0		308.0
Net income										587.0		531.0		484.0
Capital expenditures										1,564.0		1,433.0		1,320.0
Total assets		17,800.0				16,700.0				17,800.0		16,700.0
Total assets		17,800.0				16,700.0				17,800.0		16,700.0
Operating Segments | Power Delivery | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Operating revenue										2,204.0		2,212.0		2,217.0
Depreciation and amortization										624.0		594.0		537.0
Interest income												4.0
Interest and related charges										265.0		265.0		244.0
Income tax expense (benefit)										158.0		334.0		307.0
Net income										586.0		527.0		482.0
Capital expenditures										1,539.0		1,439.0		1,313.0
Total assets		17.6				16.6				17.6		16.6
Total assets		17.6				16.6				17.6		16.6
Operating Segments | Power Generation
Segment Reporting Information [Line Items]
Operating revenue										7,115.0		6,686.0		6,757.0
Depreciation and amortization										746.0		747.0		662.0
Impairment of assets and related charges										1.0
Gains on sales of assets										6.0				4.0
Equity in earnings of equity method investees										18.0		(181.0)		(16.0)
Interest income										90.0		92.0		74.0
Interest and related charges										374.0		342.0		290.0
Income tax expense (benefit)										294.0		373.0		279.0
Net income										1,254.0		1,181.0		1,397.0
Investment in equity method investees		82.0				81.0				82.0		81.0
Capital expenditures										1,321.0		2,275.0		2,440.0
Total assets		28,200.0				29,000.0				28,200.0		29,000.0
Total assets		28,200.0				29,000.0				28,200.0		29,000.0
Operating Segments | Power Generation | Virginia Electric and Power Company
Segment Reporting Information [Line Items]
Operating revenue										5,630.0		5,344.0		5,390.0
Depreciation and amortization										533.0		547.0		488.0
Interest income										9.0		15.0
Interest and related charges										250.0		232.0		219.0
Income tax expense (benefit)										220.0		534.0		524.0
Net income										1,008.0		939.0		909.0
Capital expenditures										1,003.0		1,290.0		$ 1,336.0
Total assets		19.4				18.6				19.4		18.6
Total assets		$ 19.4				$ 18.6				$ 19.4		$ 18.6

[1] See Note 9 for amounts attributable to related parties.

[2] See Note 24 for amounts attributable to related parties.

[3] See Note 24 for amounts attributable to affiliates.