Net Income (Loss) Per Common Share (Calculation Of Net Income (Loss) Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income (Loss) Per Common Share [Abstract]
Net income (loss) attributable to Frontier common shareholders	$ (133)	$ (134)	$ (80)	$ (240)	$ (156)	$ (81)	$ (28)	$ (51)	$ (587)	$ (316)	$ 133
Less: Dividends paid on unvested restricted stock awards									(3)	(3)	(3)
Total basic and diluted net income (loss) attributable to Frontier common shareholders									$ (590)	$ (319)	$ 130
Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares)									1,172,131	1,091,798	1,001,812
Less: Weighted average unvested restricted stock awards (in shares)									(8,032)	(7,192)	(7,394)
Total weighted average shares outstanding - basic (in shares)									1,164,099	1,084,606	994,418
Basic net income (loss) per share attributable to Frontier common shareholders	$ (0.12)	$ (0.12)	$ (0.07)	$ (0.21)	$ (0.14)	$ (0.07)	$ (0.03)	$ (0.05)	$ (0.51)	$ (0.29)	$ 0.13
Effect of dilutive shares (in shares)											3,744
Total weighted average shares outstanding - diluted (in shares)									1,164,099	1,084,606	998,162
Diluted net income (loss) per share attributable to Frontier common shareholders									$ (0.51)	$ (0.29)	$ 0.13