Equity (Schedule of Changes in AOCI by Component Net of Tax) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 20,107
Ending balance	31,994	$ 20,107
Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	13,047	12,224	$ 11,865
Ending balance	13,989	13,047	12,224
Deferred Gains and Losses on Derivatives-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(235)	(302)
Other comprehensive income before reclassifications: gains (losses)	(110)	30
Amounts reclassified from AOCI: (gains) losses	(62)	102
Net current period other comprehensive income (loss)	(172)	132
Cumulative-effect of changes in accounting principle		(64)
Less other comprehensive income (loss) attributable to noncontrolling interest		1
Ending balance	(407)	(235)	(302)
Deferred Gains and Losses on Derivatives-Hedging Activities \| Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(13)	(12)
Other comprehensive income before reclassifications: gains (losses)	(22)	1
Amounts reclassified from AOCI: (gains) losses	1	1
Net current period other comprehensive income (loss)	(21)	2
Cumulative-effect of changes in accounting principle		(3)
Ending balance	(34)	(13)	(12)
Deferred Gains and Losses on Derivatives-Hedging Activities \| Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(25)	(23)
Other comprehensive income before reclassifications: gains (losses)	(61)	(16)
Amounts reclassified from AOCI: (gains) losses	5	19
Net current period other comprehensive income (loss)	(56)	3
Cumulative-effect of changes in accounting principle	1	(5)
Less other comprehensive income (loss) attributable to noncontrolling interest	(1)
Ending balance	(81)	(25)	(23)
Unrealized Gains and Losses on Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	2	747
Other comprehensive income before reclassifications: gains (losses)	39		(18)
Amounts reclassified from AOCI: (gains) losses	(4)		5
Net current period other comprehensive income (loss)	35		(13)
Cumulative-effect of changes in accounting principle		(732)
Ending balance	37	2	747
Unrealized Gains and Losses on Investment Securities \| Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1	74
Other comprehensive income before reclassifications: gains (losses)	5	0
Amounts reclassified from AOCI: (gains) losses	(1)	0
Net current period other comprehensive income (loss)	4	0
Cumulative-effect of changes in accounting principle		(73)
Ending balance	5	1	74
Unrealized Gains and Losses on Investment Securities \| Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect of changes in accounting principle		(21)
Unrecognized Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,465)	(1,101)
Other comprehensive income before reclassifications: gains (losses)	(22)	(215)
Amounts reclassified from AOCI: (gains) losses	66	78
Net current period other comprehensive income (loss)	44	(137)
Cumulative-effect of changes in accounting principle		(227)
Ending balance	(1,421)	(1,465)	(1,101)
Unrecognized Pension and Other Postretirement Benefit Costs \| Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(144)	(75)
Other comprehensive income before reclassifications: gains (losses)	33	(52)
Amounts reclassified from AOCI: (gains) losses	5	4
Net current period other comprehensive income (loss)	38	(48)
Cumulative-effect of changes in accounting principle	0
Less other comprehensive income (loss) attributable to noncontrolling interest	0
Ending balance	(106)	(144)	(75)
Other Comprehensive Loss From Equity Method Investee
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(2)	(3)
Other comprehensive income before reclassifications: gains (losses)	0	1
Amounts reclassified from AOCI: (gains) losses	0
Net current period other comprehensive income (loss)	0	1
Ending balance	(2)	(2)	(3)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,700)	(659)
Other comprehensive income before reclassifications: gains (losses)	(93)	(202)
Amounts reclassified from AOCI: (gains) losses	0	185
Net current period other comprehensive income (loss)	(93)	(17)
Cumulative-effect of changes in accounting principle		(1,023)
Less other comprehensive income (loss) attributable to noncontrolling interest		1
Ending balance	(1,793)	(1,700)	(659)
Accumulated Other Comprehensive Income (Loss) \| Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(12)	62	46
Other comprehensive income before reclassifications: gains (losses)	(17)	1
Amounts reclassified from AOCI: (gains) losses	0	1
Net current period other comprehensive income (loss)	(17)	2
Cumulative-effect of changes in accounting principle		(76)
Ending balance	(29)	(12)	62
Accumulated Other Comprehensive Income (Loss) \| Dominion Energy Gas Holdings, LLC
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(169)	(98)
Other comprehensive income before reclassifications: gains (losses)	(28)	(68)
Amounts reclassified from AOCI: (gains) losses	10	23
Net current period other comprehensive income (loss)	(18)	(45)
Cumulative-effect of changes in accounting principle	1	(26)
Less other comprehensive income (loss) attributable to noncontrolling interest	(1)
Ending balance	$ (187)	$ (169)	$ (98)

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