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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Loss Per Share [Abstract]
Total basic net loss attributable to Frontier common shareholders	$ (5,317)	$ (72)	$ (5,404)	$ (105)
Total diluted net loss attributable to Frontier common shareholders	$ (5,317)	$ (72)	$ (5,404)	$ (105)
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	105,314	80,201	105,377	79,429
Less: Weighted average unvested restricted stock awards (in shares)	(1,196)	(2,175)	(1,390)	(1,744)
Total weighted average shares outstanding - basic (in shares)	104,118	78,026	103,987	77,685
Basic net loss per share attributable to Frontier common shareholders	$ (51.07)	$ (0.92)	$ (51.97)	$ (1.35)
Total weighted average shares outstanding - diluted (in shares)	104,118	78,026	103,987	77,685
Diluted net loss per share attributable to Frontier common shareholders	$ (51.07)	$ (0.92)	$ (51.97)	$ (1.35)