Employee Benefit Plans (Net Periodic Benefit Cost (Credit)) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 43	$ 40	$ 86	$ 80
Interest cost		90	98	181	199
Expected return on plan assets		(192)	(176)	(385)	(353)
Amortization of prior service cost (credit)		1	1	1	1
Amortization of net actuarial loss		48	43	97	82
Settlement and curtailment	[1]	2	71	2	73
Net periodic benefit cost (credit)		(8)	77	(18)	82
Pension Benefits | Dominion Energy Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost		2	4	3	8
Interest cost		2	8	5	16
Expected return on plan assets		(14)	(39)	(28)	(78)
Amortization of prior service cost (credit)		0	0	0	0
Amortization of net actuarial loss		2	5	4	10
Settlement and curtailment	[2]	0	1	0	1
Net periodic benefit cost (credit)		(8)	(21)	(16)	(43)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		7	6	14	13
Interest cost		15	17	30	34
Expected return on plan assets		(39)	(35)	(78)	(68)
Amortization of prior service cost (credit)		(13)	(13)	(25)	(26)
Amortization of net actuarial loss		2	3	3	7
Settlement and curtailment	[1]	0	42	0	42
Net periodic benefit cost (credit)		(28)	20	(56)	2
Other Postretirement Benefits | Dominion Energy Gas Holdings, LLC
Defined Benefit Plan Disclosure [Line Items]
Service cost		0	1	1	2
Interest cost		1	2	2	5
Expected return on plan assets		(5)	(7)	(10)	(14)
Amortization of prior service cost (credit)		(1)	(1)	(2)	(2)
Amortization of net actuarial loss		1	1	1	2
Settlement and curtailment	[2]	0	1	0	1
Net periodic benefit cost (credit)		$ (4)	$ (3)	$ (8)	$ (6)

[1] 2019 amounts relate primarily to a voluntary retirement program.

[2] 2019 amounts relate to a voluntary retirement program.