Commitments and Contingencies (Narrative) (Detail)	1 Months Ended				3 Months Ended		6 Months Ended
	Jul. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) State MW	Mar. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) State Product MW	Jun. 30, 2018 USD ($)
Loss Contingencies [Line Items]
Number of states required to reduce emissions under CSAPR | State					28		28
Number of MGP decommissioned sites that contain residues of byproduct chemicals | Product							4
Estimated environmental remediation activities at MGP sites							$ 10,000,000
Estimated increase in remediation costs for Congaree River site							8,000,000
Environmental remediation costs recognized in regulatory assets					$ 23,000,000		23,000,000
Impairment of assets and other charges						$ 105,000,000	371,000,000	$ 4,000,000
Asset impairment charges after tax						79,000,000
Customer refundable fees, alternative plan		$ 2,390,000,000			3,546,000,000		3,546,000,000
Regulatory liability for refunds to natural gas customers						2,000,000
Regulatory liability for refunds to natural gas customers, net of tax						2,000,000
Regulatory asset impairment charges committed to forgo recovery						264,000,000
Tax charge related to regulatory assets committed to forgo recovery						198,000,000
Transmission assets related to BLRA capital costs					323,000,000		323,000,000
Transmission assets related to BLRA regulatory assets					27,000,000		27,000,000
Reserves		11,000,000			278,000,000		278,000,000
Legal expense					100,000,000		266,000,000
Legal expense, net of taxes					75,000,000		200,000,000
Escrow amount		2,000,000,000.0
Credit in future electric rate relief for ratepayer case		2,000,000,000.0
Cash payment related to Ratepayer Case		115,000,000
Amount claimed by plantiffs in legal matter			$ 75,000,000
Proportionate ownership share in project			100.00%	100.00%
Proposed assessment amount from SCDOR audit				$ 410,000,000
Estimate of aggregate amount of subcontractor and vendor liens filed							285,000,000
Reduction of liens filed							$ 60,000,000
Percentage share of reduction of liens filed							55.00%
Nuclear Insurance
Maximum liability protection per nuclear incident amount							$ 14,000,000,000.0
Amount of coverage purchased from commercial insurance pools					450,000,000		450,000,000
Maximum assessment for premiums on insurance policy							92,000,000
Maximum liability protection per nuclear incident amount per year							$ 14,000,000
Inflation adjustment period for nuclear insurance							5 years
NEIL maximum insurance coverage to nuclear facility for property damage and outage costs					2,750,000,000		$ 2,750,000,000
NEIL maximum insurance coverage to nuclear facility for property damage and outage costs from non-nuclear event							2,330,000,000
NEIL aggregate maximum loss for any single loss occurrence					$ 2,750,000,000		2,750,000,000
NEIL maximum retrospective premium assessment							24,000,000
EMANI maximum insurance coverage for Summer station unit 1 for property damage and outage costs from non-nuclear event							415,000,000
EMANI maximum retrospective premium assessment							2,000,000
Dominion Energy South Carolina, Inc.
Loss Contingencies [Line Items]
Estimate of aggregate amount of subcontractor and vendor liens filed							$ 33,000,000
Subsequent Event
Loss Contingencies [Line Items]
Cash payment related to Ratepayer Case	$ 117,000,000
Property with net value transferred	$ 42,000,000
DESC Ratepayer Case
Loss Contingencies [Line Items]
Customer refundable fees, alternative plan						1,000,000,000.0
Customer refund fees alternative plan net of tax						$ 756,000,000
Customer refunded estimated period						11 years
Previous existing regulatory liability						$ 1,000,000,000.0
Previous existing regulatory liability, years						20 years
Minimum [Member]
Loss Contingencies [Line Items]
Power Generation Capacity Megawatts | MW					25		25
Estimated aggregate value of certain real estate		60,000,000
Maximum [Member]
Loss Contingencies [Line Items]
Estimated aggregate value of certain real estate		$ 85,000,000
Nuclear Insurance
Amount that could be assessed for each licensed reactor					$ 138,000,000		$ 138,000,000
Amount that could be assessed for each licensed reactor per reactor							$ 21,000,000