Employee Benefit Plans - EEGH - Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	$ 742	$ 664
Employer contributions	3	2
Actual return on plan assets	40	122
Benefits paid	(49)	(55)
Ending balance	744	742	$ 664
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	673	672
Service cost	7	8	9
Interest cost	21	27	24
Actuarial loss	(61)	(12)
Settlement	0	0
Benefits paid	(49)	(55)
Ending balance	758	673	672
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Plan assets at fair value, end of year	744	742	664	$ 744	$ 742		$ 664
Less - Benefit obligation, end of year	673	673	672	758	673		$ 672
Defined Benefit Plan, Funded (Unfunded) Status of Plan				(14)	69
Assets for Plan Benefits, Defined Benefit Plan				$ 20	$ 76
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				2.59%	3.24%		4.21%
Eastern Energy Gas Holdings, LLC [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Accumulated Benefit Obligation					$ 279
Eastern Energy Gas Holdings, LLC [Member] | Pension Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	686	1,656
Dominion Energy Gas Restructuring		(1,084)
Employer contributions		0
Actual return on plan assets		129
Benefits paid		(15)
Ending balance		686	1,656
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	295	730
Dominion Energy Gas Restructuring		(468)
Service cost		6
Interest cost		11
Actuarial loss		30
Settlement		1
Benefits paid		(15)
Ending balance		295	730
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Plan assets at fair value, end of year	686	686	1,656		686		$ 1,656
Less - Benefit obligation, end of year	295	295	730		295		730
Defined Benefit Plan, Funded (Unfunded) Status of Plan					391
Assets for Plan Benefits, Defined Benefit Plan					$ 391
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					3.63%	4.10%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase					4.64%
Eastern Energy Gas Holdings, LLC [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	227	311
Dominion Energy Gas Restructuring		(126)
Employer contributions		12
Actual return on plan assets		38
Benefits paid		(8)
Ending balance		227	311
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	121	256
Dominion Energy Gas Restructuring		(135)
Service cost		1
Interest cost		5
Actuarial loss		1
Settlement		1
Benefits paid		(8)
Ending balance		121	256
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Plan assets at fair value, end of year	227	227	311		$ 227		311
Less - Benefit obligation, end of year	$ 121	$ 121	$ 256		121		$ 256
Defined Benefit Plan, Funded (Unfunded) Status of Plan					106
Assets for Plan Benefits, Defined Benefit Plan					$ 106
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					3.44%	4.05%