Accumulated Other Comprehensive Income (Loss) (Schedule of Changes in AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			$ 26,117
Total other comprehensive income (loss)		$ 24	$ (36)	101		$ (223)
Ending balance		26,906		26,906
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		15,064	13,944	14,557	[2]	13,989
Total other comprehensive income (loss)		(3)	5	16		(36)
Ending balance		15,617	14,315	15,617		14,315
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(371)	(644)	(419)		(407)
Other comprehensive income before reclassifications: gains (losses)		(2)	10	21		(254)
Amounts reclassified from AOCI: (gains) losses	[3]	10	188	35		215
Total other comprehensive income (loss)		8	198	56		(39)
Ending balance		(363)	(446)	(363)		(446)
Deferred Gains and Losses on Derivatives-Hedging Activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(39)	(78)	(60)		(34)
Other comprehensive income before reclassifications: gains (losses)		(2)	5	18		(39)
Amounts reclassified from AOCI: (gains) losses	[4]	0	1	1		1
Total other comprehensive income (loss)		(2)	6	19		(38)
Ending balance		(41)	(72)	(41)		(72)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		41	51	62		37
Other comprehensive income before reclassifications: gains (losses)		4	4	(15)		32
Amounts reclassified from AOCI: (gains) losses	[3]	(3)	(1)	(5)		(15)
Total other comprehensive income (loss)		1	3	(20)		17
Ending balance		42	54	42		54
Unrealized Gains and Losses on Investment Securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		6	8	8		5
Other comprehensive income before reclassifications: gains (losses)		0	0	(2)		4
Amounts reclassified from AOCI: (gains) losses	[4]	(1)	(1)	(1)		(2)
Total other comprehensive income (loss)		(1)	(1)	(3)		2
Ending balance		5	7	5		7
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,309)	(1,385)	(1,359)		(1,421)
Other comprehensive income before reclassifications: gains (losses)		(1)	(261)	5		(262)
Amounts reclassified from AOCI: (gains) losses	[3]	19	23	63		60
Total other comprehensive income (loss)		18	(238)	68		(202)
Ending balance		(1,291)	(1,623)	(1,291)		(1,623)
Other Comprehensive Loss From Equity Method Investees
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1)	(2)	(1)		(2)
Other comprehensive income before reclassifications: gains (losses)		(3)	1	(3)		1
Amounts reclassified from AOCI: (gains) losses	[3]	0	0	0		0
Total other comprehensive income (loss)		(3)	1	(3)		1
Ending balance		(4)	(1)	(4)		(1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1,640)	(1,980)	(1,717)		(1,793)
Other comprehensive income before reclassifications: gains (losses)		(2)	(246)	8		(483)
Amounts reclassified from AOCI: (gains) losses	[3]	26	210	93		260
Total other comprehensive income (loss)		24	(36)	101		(223)
Ending balance		(1,616)	(2,016)	(1,616)		(2,016)
Accumulated Other Comprehensive Income (Loss) | Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(33)	(70)	(52)		(29)
Other comprehensive income before reclassifications: gains (losses)		(2)	5	16		(35)
Amounts reclassified from AOCI: (gains) losses	[4]	(1)	0	0		(1)
Total other comprehensive income (loss)		(3)	5	16		(36)
Ending balance		$ (36)	$ (65)	$ (36)		$ (65)

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

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

[4] Amounts are allocated as follows within Virginia Power’s Consolidated Statements of Income; deferred gains and losses on derivatives – hedging activities are recorded to interest and related charges, unrealized gains and losses on investment securities are recorded to other income and associated tax amounts are recorded to income tax expense.