Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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+ Details

Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Income Taxes [Line Items]
Weighted average rate reversal of deferred taxes to originate the deferred tax liability			35.00%
Deferred tax benefit			$ 21
Income tax expense (benefit) from discontinued operations	$ 4	$ (593)	11	$ (562)
Atlantic Coast Pipeline \| Supply Header Project \| Discontinued Operations
Income Taxes [Line Items]
Income taxes charge					$ 81
Virginia Electric and Power Company
Income Taxes [Line Items]
Deferred tax benefit			$ 16