Net Loss Per Share (Calculation Of Net Income (Loss) Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net Loss Per Share [Abstract]
Net loss attributable to Frontier common shareholders	$ (72)	$ (715)	$ (105)	$ (844)
Less: Dividends paid on unvested restricted stock awards		(1)		(2)
Total basic net loss attributable to Frontier common shareholders	(72)	(716)	(105)	(846)
Effect of loss related to dilutive stock units		(2)		(2)
Total diluted net loss attributable to Frontier common shareholders	$ (72)	$ (718)	$ (105)	$ (848)
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	80,201	78,531	79,429	78,365
Less: Weighted average unvested restricted stock awards (in shares)	(2,175)	(736)	(1,744)	(686)
Total weighted average shares outstanding - basic (in shares)	78,026	77,795	77,685	77,679
Basic net loss per share attributable to Frontier common shareholders	$ (0.92)	$ (9.20)	$ (1.35)	$ (10.88)
Effect of dilutive stock units (in shares)		156		156
Total weighted average shares outstanding - diluted (in shares)	78,026	77,951	77,685	77,835
Diluted net loss per share attributable to Frontier common shareholders	$ (0.92)	$ (9.21)	$ (1.35)	$ (10.89)