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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Loss Per Share [Abstract]
Net loss attributable to Frontier common shareholders	$ (92)	$ (134)	$ (936)	$ (454)
Less: Dividends paid on unvested restricted stock awards		(1)	(2)	(3)
Total basic net loss attributable to Frontier common shareholders	(92)	(135)	(938)	(457)
Effect of loss related to dilutive stock units			(2)
Total diluted net loss attributable to Frontier common shareholders	$ (92)	$ (135)	$ (940)	$ (457)
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	78,488	78,205	78,399	78,134
Less: Weighted average unvested restricted stock awards (in shares)	(691)	(593)	(685)	(526)
Total weighted average shares outstanding - basic (in shares)	77,797	77,612	77,714	77,608
Basic net loss per share attributable to Frontier common shareholders	$ (1.19)	$ (1.73)	$ (12.06)	$ (5.87)
Effect of dilutive stock units (in shares)			161
Total weighted average shares outstanding - diluted (in shares)	77,797	77,612	77,875	77,608
Diluted net loss per share attributable to Frontier common shareholders	$ (1.19)	$ (1.73)	$ (12.07)	$ (5.87)