Equity (Schedule of Changes in AOCI Net of Tax and Reclassifications out of AOCI by Component) (Detail) - USD ($) $ in Millions			1 Months Ended	12 Months Ended
		Nov. 30, 2020	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				$ 26,117
Operating Revenue				13,964	$ 14,172	$ 14,401
Interest and related charges				1,354	1,377	1,486
Income tax expense		$ 336	$ 173	425	83	209
Total, net of tax				(2,673)	(1,328)	(660)
Total other comprehensive income (loss)				259	76	(93)
Ending balance			27,308	27,308	26,117
Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				14,557	13,989	13,047
Operating Revenue	[1]			7,470	7,763	8,108
Interest and related charges	[1]			534	516	524
Total				(2,109)	(1,250)	(1,413)
Income tax expense				397	229	264
Total other comprehensive income (loss)				11	(23)	(17)
Ending balance			15,980	15,980	14,557	13,989
Commodity
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				(1)	16
Total, net of tax				1
Total other comprehensive income (loss)				1	(17)
Ending balance					(1)	16
Commodity | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Operating Revenue					(25)
Purchased gas				1	4
Income before income taxes					(2)
Total				1	(23)
Income tax expense					6
Total, net of tax					(17)
Interest rate
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				(418)	(426)
Other comprehensive income before reclassifications: gains (losses)				15	(231)
Total, net of tax				45
Total other comprehensive income (loss)				60	8
Ending balance			(358)	(358)	(418)	(426)
Interest rate | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Income before income taxes					236
Interest and related charges				60	83
Total				60	319
Income tax expense				(15)	(80)
Total, net of tax					239
Foreign currency exchange rate
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance					3
Other comprehensive income before reclassifications: gains (losses)					(8)
Total other comprehensive income (loss)					(3)
Ending balance						3
Foreign currency exchange rate | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Income before income taxes					6
Total					6
Income tax expense					(1)
Total, net of tax					5
Total Derivative-Hedging Activities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[2]			(419)	(407)
Other comprehensive income before reclassifications: gains (losses)	[2]			15	(239)
Total, net of tax	[2]			46
Total other comprehensive income (loss)	[2]			61	(12)
Ending balance	[2]		(358)	(358)	(419)	(407)
Total Derivative-Hedging Activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[3]			(60)	(34)
Other comprehensive income before reclassifications: gains (losses)	[3]			13	(28)
Total other comprehensive income (loss)	[3]			15	(26)
Ending balance	[3]		(45)	(45)	(60)	(34)
Total Derivative-Hedging Activities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Operating Revenue	[2]				(25)
Purchased gas	[2]			1	4
Income before income taxes	[2]				240
Interest and related charges	[2]			60	83
Total	[2]			61	302
Income tax expense	[2]			(15)	(75)
Total, net of tax	[2]				227
Total Derivative-Hedging Activities | Amounts reclassified from AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Interest and related charges	[3]			3	2
Total	[3]			3	2
Income tax expense	[3]			(1)
Total, net of tax	[3]			2	2
Investment Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[4]			62	37
Other comprehensive income before reclassifications: gains (losses)	[4]			(7)	43
Total, net of tax	[4]			(18)
Total other comprehensive income (loss)	[4]			(25)	25
Ending balance	[4]		37	37	62	37
Investment Securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[5]			8	5
Other comprehensive income before reclassifications: gains (losses)	[5]			(2)	6
Total other comprehensive income (loss)	[5]			(4)	3
Ending balance	[5]		4	4	8	5
Investment Securities | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Other income	[4]			(23)	(24)
Total	[4]			(23)	(24)
Income tax expense	[4]			5	6
Total, net of tax	[4]				(18)
Investment Securities | Amounts reclassified from AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Other income	[5]			(3)	(4)
Total	[5]			(3)	(4)
Income tax expense	[5]			1	1
Total, net of tax	[5]			(2)	(3)
Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[6]			(1,359)	(1,421)
Other comprehensive income before reclassifications: gains (losses)	[6]			144	25
Total, net of tax	[6]			82
Total other comprehensive income (loss)	[6]			226	62
Ending balance	[6]		(1,133)	(1,133)	(1,359)	(1,421)
Pension and Other Postretirement Benefit Costs | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Other income	[6]			111	50
Total	[6]			111	50
Income tax expense	[6]			(29)	(13)
Total, net of tax	[6]				37
Equity Method Investees
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	[7]			(1)	(2)
Other comprehensive income before reclassifications: gains (losses)	[7]			(3)	1
Total other comprehensive income (loss)	[7]			(3)	1
Ending balance	[7]		(4)	(4)	(1)	(2)
AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				(1,717)	(1,793)
Other comprehensive income before reclassifications: gains (losses)				149	(170)
Total, net of tax				110
Total other comprehensive income (loss)				259	76	(93)
Ending balance			(1,458)	(1,458)	(1,717)	(1,793)
AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				(52)	(29)	(12)
Other comprehensive income before reclassifications: gains (losses)				11	(22)
Total other comprehensive income (loss)				11	(23)	(17)
Ending balance			(41)	(41)	(52)	(29)
AOCI | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income Loss [Line Items]
Operating Revenue					(25)
Purchased gas				1	4
Income before income taxes					240
Interest and related charges				60	83
Other income				88	26
Total				149	328
Income tax expense				(39)	(82)
Total, net of tax					246
AOCI | Amounts reclassified from AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Interest and related charges				3	2
Other income				(3)	(4)
Total					(2)
Income tax expense					1
Total, net of tax					(1)
Interest Rate | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance				(60)	(34)
Other comprehensive income before reclassifications: gains (losses)				13	(28)
Total other comprehensive income (loss)				15	(26)
Ending balance			$ (45)	(45)	(60)	$ (34)
Interest Rate | Amounts reclassified from AOCI | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Interest and related charges				3	2
Total				3	2
Income tax expense				(1)
Total, net of tax				$ 2	$ 2

[1] See Note 25 for amounts attributable to affiliates.

[2] Net of $119 million and $141 million tax at December 31, 2021 and 2020, respectively.

[3]  Net of $16 million and $21 million tax at December 31, 2021 and 2020, respectively.

[4] Net of $(10) million and $(21) million tax at December 31, 2021 and 2020, respectively.

[5] Net of $(2) million and $(3) million tax at December 31, 2021 and 2020, respectively.

[6] Net of $396 million and $478 million tax at December 31, 2021 and 2020, respectively.

[7] Net of $1 million and $— million tax at December 31, 2021 and 2020, respectively.