Income Taxes (Schedule Of Components Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2021	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Current [Abstract]
State	$ 12	$ 8	$ 10	$ (7)
Total Current	12	8	10	(7)
Deferred [Abstract]
Federal	(116)	(84)	58	125
State	(32)	162	20	40
Total Deferred	(148)	78	78	165
Total income tax expense (benefit)	(136)	86	88	158
Income taxes charged (credited) to equity of Frontier [Abstract]
Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability		19	6	8
Total income tax expense (benefit)	$ (136)	$ 105	$ 94	$ 166