Income Taxes (Narrative) (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	Dec. 31, 2017
Income Taxes [Line Items]
Percentage of interest expense adjusted to taxable income			30.00%
State deferred income tax expense (benefit)			$ (19)	$ 72	$ (50)
Current federal income taxes			(117)	(395)	(36)
Taxes charged to common shareholders' equity					215
Income tax expense	$ 336	$ 173	$ 425	$ 83	$ 209
Federal statutory income tax rate			21.00%	21.00%	21.00%	35.00%
Deferred income tax expense (benefit)			$ 425	$ 439	$ 186
Income tax benefit associated with remeasurement of state deferred taxes			(43)	(44)	(119)
Income tax expense attributable to noncontrolling interest				55
Unrecognized tax benefits that would impact effective tax rate		72	72	140	141
Maximum
Income Taxes [Line Items]
Decrease in Unrecognized tax benefits due to settlement negotiations and expiration of statutes of limitations		23	23
Amount that earnings could potentially increase if changes were to occur			9
Virginia Electric and Power Company
Income Taxes [Line Items]
State deferred income tax expense (benefit)			118	7	22
Current federal income taxes			54	435	344
Income tax expense			$ 397	$ 229	$ 264
Federal statutory income tax rate			21.00%	21.00%	21.00%
Increase (Decrease) in tax expense as a result of changes in unrecognized tax benefits					$ (2)
Deferred income tax expense (benefit)			$ 224	$ (246)	(140)
Income tax benefit associated with remeasurement of state deferred taxes			0	0	0
Virginia Electric and Power Company | Maximum
Income Taxes [Line Items]
Unrecognized tax benefits that would impact effective tax rate					1
SCANA
Income Taxes [Line Items]
Deferred income tax expense (benefit)			194
Discontinued Operations
Income Taxes [Line Items]
Income tax expense			188	(204)	142
Increase (Decrease) in tax expense as a result of changes in unrecognized tax benefits				5
Unrecognized tax benefits that would impact effective tax rate		$ 33	33
Discontinued Operations | Maximum
Income Taxes [Line Items]
Increase (Decrease) in tax expense as a result of changes in unrecognized tax benefits					(1)
Continuing Operations
Income Taxes [Line Items]
Increase (Decrease) in tax expense as a result of changes in unrecognized tax benefits			(34)	(6)	$ 3
Deferred income tax expense (benefit)			(21)
Continuing Operations | Virginia Electric and Power Company
Income Taxes [Line Items]
Deferred income tax expense (benefit)			(16)
Continuing Operations | SCANA
Income Taxes [Line Items]
Increase (Decrease) in tax expense as a result of changes in unrecognized tax benefits			(38)
Cove Point
Income Taxes [Line Items]
Ownership interest percentage of limited partner interests					25.00%
Current federal income taxes					$ 362
Benefit for deferred income taxes					147
Federal tax credits					208
Atlantic Coast Pipeline | Discontinued Operations | Supply Header Project
Income Taxes [Line Items]
Income tax charge				81
Federal
Income Taxes [Line Items]
Deferred income tax expense					$ 48
State
Income Taxes [Line Items]
Income tax benefit associated with remeasurement of state deferred taxes				45
GT&S Transaction
Income Taxes [Line Items]
State deferred income tax expense (benefit)				18
GT&S Transaction | Discontinued Operations
Income Taxes [Line Items]
Income tax benefit related to finalizing income tax returns			14
Income tax expense (benefit) on non-deductible goodwill written off				$ 236
Q-Pipe Group | Discontinued Operations
Income Taxes [Line Items]
Income tax expense (benefit) on non-deductible goodwill written off			$ 36