Accumulated Other Comprehensive Income (Schedule of Changes in AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			$ 31,994
Total other comprehensive income (loss)		$ (36)	$ (94)	(223)	$ (77)
Ending balance		26,336		26,336
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		13,944	12,964	13,989	13,047
Total other comprehensive income (loss)		5	(15)	(36)	(29)
Ending balance		14,315	13,550	14,315	13,550
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(644)	(389)	(407)	(235)
Other comprehensive income before reclassifications: gains (losses)		10	(107)	(254)	(209)
Amounts reclassified from AOCI: (gains) losses	[2]	188	(6)	215	(58)
Total other comprehensive income (loss)		198	(113)	(39)	(267)
Ending balance		(446)	(502)	(446)	(502)
Deferred Gains and Losses on Derivatives-Hedging Activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(78)	(30)	(34)	(13)
Other comprehensive income before reclassifications: gains (losses)		5	(16)	(39)	(34)
Amounts reclassified from AOCI: (gains) losses	[3]	1	0	1	1
Total other comprehensive income (loss)		6	(16)	(38)	(33)
Ending balance		(72)	(46)	(72)	(46)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		51	30	37	2
Other comprehensive income before reclassifications: gains (losses)		4	8	32	37
Amounts reclassified from AOCI: (gains) losses	[2]	(1)	(4)	(15)	(5)
Total other comprehensive income (loss)		3	4	17	32
Ending balance		54	34	54	34
Unrealized Gains and Losses on Investment Securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		8	4	5	1
Other comprehensive income before reclassifications: gains (losses)		0	1	4	5
Amounts reclassified from AOCI: (gains) losses	[3]	(1)	0	(2)	(1)
Total other comprehensive income (loss)		(1)	1	2	4
Ending balance		7	5	7	5
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,385)	(1,322)	(1,421)	(1,465)
Other comprehensive income before reclassifications: gains (losses)		(261)	(4)	(262)	109
Amounts reclassified from AOCI: (gains) losses	[2]	23	20	60	50
Total other comprehensive income (loss)		(238)	16	(202)	159
Ending balance		(1,623)	(1,306)	(1,623)	(1,306)
Other Comprehensive Loss From Equity Method Investees
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(2)	(2)	(2)	(2)
Other comprehensive income before reclassifications: gains (losses)		1	(1)	1	(1)
Amounts reclassified from AOCI: (gains) losses	[2]	0	0	0	0
Total other comprehensive income (loss)		1	(1)	1	(1)
Ending balance		(1)	(3)	(1)	(3)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,980)	(1,683)	(1,793)	(1,700)
Other comprehensive income before reclassifications: gains (losses)		(246)	(104)	(483)	(64)
Amounts reclassified from AOCI: (gains) losses	[2]	210	10	260	(13)
Total other comprehensive income (loss)		(36)	(94)	(223)	(77)
Ending balance		(2,016)	(1,777)	(2,016)	(1,777)
Accumulated Other Comprehensive Income (Loss) | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(70)	(26)	(29)	(12)
Other comprehensive income before reclassifications: gains (losses)		5	(15)	(35)	(29)
Amounts reclassified from AOCI: (gains) losses	[3]	0	0	(1)	0
Total other comprehensive income (loss)		5	(15)	(36)	(29)
Ending balance		$ (65)	$ (41)	$ (65)	$ (41)

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2019 has been derived from the audited Consolidated Balance Sheet at that date.

[2] See table below for details about these reclassifications.

[3] See table below for details about these reclassifications. Virginia Power’s reclassifications out of AOCI were immaterial for both the three and nine months ended September 30, 2019