Asset Retirement Obligations - MEC - Change in Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 1,328	$ 1,340
Change in estimated costs	54	2
Additions	56	32
Retirements	(64)	(122)
Accretion	54	47
Ending Balance	1,428	1,328
Total ARO liability	1,428	1,328
MEC
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	707	787
Change in estimated costs	56	(27)
Additions	3	2
Retirements	(21)	(85)
Accretion	33	30
Ending Balance	778	707
Other current liabilities	10	24
Other long-term liabilities	768	683
Total ARO liability	778	707
Fossil-fueled generating facilities
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	396
Ending Balance	402	396
Total ARO liability	402	396
Fossil-fueled generating facilities | MEC
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	76
Ending Balance	62	76
Total ARO liability	$ 62	$ 76