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, 2022	Dec. 31, 2020
Current [Abstract]
Federal				$ (12)
State	$ 12	$ 8	$ (7)	19
Total Current	12	8	(7)	7
Deferred [Abstract]
Federal	(116)	(84)	125	(84)
State	(32)	162	40	(7)
Total Deferred	(148)	78	165	(91)
Total income tax expense (benefit)	(136)	86	158	(84)
Income taxes charged (credited) to equity of Frontier [Abstract]
Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability		19	8	35
Total income taxes charged (credited) to equity of Frontier				35
Total income tax benefit	$ (136)	$ 105	$ 166	$ (49)