Net Income (Loss) Per Common Share (Reconciliation Of Net Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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]
Total basic net income (loss) attributable to Frontier common shareholders		$ 414
Total diluted net income (loss) attributable to Frontier common shareholders		$ 414
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)		244,405
Total weighted average shares outstanding - basic		244,405
Basic net income (loss) per share attributable to Frontier common shareholders		$ 1.69
Total weighted average shares outstanding - basic		244,405
Effect of dilutive stock units (in shares)		1,480
Total weighted average shares outstanding - diluted		245,885
Diluted net income (loss) per share attributable to Frontier common shareholders		$ 1.68
Predecessor [Member]
Total basic net income (loss) attributable to Frontier common shareholders	$ 4,541		$ (402)	$ (5,911)
Total diluted net income (loss) attributable to Frontier common shareholders	$ 4,541		$ (402)	$ (5,911)
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	104,799		104,944	105,356
Less: Weighted average unvested restricted stock awards	(215)		(477)	(1,291)
Total weighted average shares outstanding - basic	104,584		104,467	104,065
Basic net income (loss) per share attributable to Frontier common shareholders	$ 43.42		$ (3.85)	$ (56.80)
Total weighted average shares outstanding - basic	104,584		104,467	104,065
Effect of dilutive stock units (in shares)	340
Total weighted average shares outstanding - diluted	104,924		104,467	104,065
Diluted net income (loss) per share attributable to Frontier common shareholders	$ 43.28		$ (3.85)	$ (56.80)