Income Taxes - EEGH - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Income Tax Expense (Benefit) Components [Line Items]
Income tax expense		$ 33	$ 1
Accrued property, income and other taxes	$ 582	537
Eastern Energy Gas Holdings, LLC [Member]
Schedule of Income Tax Expense (Benefit) Components [Line Items]
Income tax expense			$ 1
Income tax benefit associated with effects of changes in tax status of subsidairies	24
Receivables from affiliates	139	362
Accrued property, income and other taxes	$ 29	$ 81