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
	Mar. 31, 2019	Mar. 31, 2018
Net Loss Per Share [Abstract]
Total basic net loss attributable to Frontier common shareholders	$ (87)	$ (33)
Total diluted net loss attributable to Frontier common shareholders	$ (87)	$ (33)
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)	105,426	78,861
Less: Weighted average unvested restricted stock awards (in shares)	(1,541)	(1,445)
Total weighted average shares outstanding - basic (in shares)	103,885	77,416
Basic net loss per share attributable to Frontier common shareholders	$ (0.84)	$ (0.44)
Total weighted average shares outstanding - diluted (in shares)	103,885	77,416
Diluted net loss per share attributable to Frontier common shareholders	$ (0.84)	$ (0.44)