Asset Retirement Obligations - EEGH - Change in Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 1,272	$ 985
Change in estimated costs	46	257
Additions	51	43
Retirements	(201)	(61)
Charge related to a voluntary retirement program	51	48
Other current liabilities	184	167
Other long-term liabilities	1,157	1,105
Ending Balance	1,341	1,272
Eastern Energy Gas Holdings, LLC [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	89	88
Change in estimated costs	(51)	0
Additions	48	0
Retirements	(3)	(3)
Disposal of Questar Pipeline Group	(16)	0
Charge related to a voluntary retirement program	4	4
Other current liabilities	36	14
Other long-term liabilities	35	75
Ending Balance	$ 71	$ 89