Asset Retirement Obligations (Schedule of Reconciliation of the Carrying Amount of AROs) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation Disclosure [Abstract]
Beginning balance		$ 628	$ 599
Liabilities incurred		7	6
Liabilities settled		(14)	(1)
Accretion expense		29	26
Revisions in estimated cash flows	[1]	81	(2)
Ending balance		$ 731	$ 628

[1] In 2023, there was an increase in estimated costs associated with certain coal-fired generating units, including revisions following the approval of closure plans for a facility previously taken out of service.