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, 2020	Dec. 31, 2019
Successor [Member]
Current [Abstract]
State		$ 8
Total Current		8
Deferred [Abstract]
Federal		(84)
State		162
Total Deferred		78
Total income tax benefit		86
Income taxes charged (credited) to equity of Frontier [Abstract]
Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability		19
Total income tax benefit		$ 105
Predecessor [Member]
Current [Abstract]
Federal			$ (12)	$ 1
State	$ 12		19	7
Total Current	12		7	8
Deferred [Abstract]
Federal	(116)		(84)	(606)
State	(32)		(7)	(13)
Total Deferred	(148)		(91)	(619)
Total income tax benefit	(136)		(84)	(611)
Income taxes charged (credited) to equity of Frontier [Abstract]
Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability			35	32
Total income taxes charged (credited) to equity of Frontier			35	32
Total income tax benefit	$ (136)		$ (49)	$ (579)