Net Earnings Per Share (Reconciliation Of Net Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Apr. 30, 2021	Sep. 30, 2021	Sep. 30, 2022
Successor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total basic net income attributable to Frontier common shareholders	$ 120	$ 126		$ 225	$ 286
Total diluted net income attributable to Frontier common shareholders	$ 120	$ 126		$ 225	$ 286
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	244,984	244,403		244,402	244,711
Total weighted average shares outstanding - basic	244,984	244,403		244,402	244,711
Basic net earnings per share attributable to Frontier common shareholders	$ 0.49	$ 0.52		$ 0.92	$ 1.17
Total weighted average shares outstanding - basic	244,984	244,403		244,402	244,711
Total weighted average shares outstanding - diluted	245,212	245,667		245,600	245,080
Diluted net earnings per share attributable to Frontier common shareholders	$ 0.49	$ 0.51		$ 0.92	$ 1.17
Successor [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of dilutive awards (in shares)	228	1,264		1,198	369
Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total basic net income attributable to Frontier common shareholders			$ 4,541
Total diluted net income attributable to Frontier common shareholders			$ 4,541
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)			104,799
Less: Weighted average unvested restricted stock awards			(215)
Total weighted average shares outstanding - basic			104,584
Basic net earnings per share attributable to Frontier common shareholders			$ 43.42
Total weighted average shares outstanding - basic			104,584
Total weighted average shares outstanding - diluted			104,924
Diluted net earnings per share attributable to Frontier common shareholders			$ 43.28
Predecessor [Member] | Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of dilutive awards (in shares)			340