Quarterly Financial Data (Schedule Of Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Revenue	$ 2,217	$ 2,251	$ 2,304	$ 2,356	$ 2,409	$ 2,524	$ 2,608	$ 1,355	$ 9,128	$ 8,896	$ 5,576
Operating income (loss)	(1,754)	309	(394)	271	255	264	311	58	(1,568)	888	745
Net income (loss) attributable to Frontier common shareholders	$ (1,082)	$ (92)	$ (715)	$ (129)	$ (133)	$ (134)	$ (80)	$ (240)	$ (2,018)	$ (587)	$ (316)
Basic net income (loss) per share attributable to Frontier common shareholders	$ (13.91)	$ (1.19)	$ (9.20)	$ (1.67)	$ (1.73)	$ (1.73)	$ (1.05)	$ (3.10)	$ (25.99)	$ (7.61)	$ (4.41)
Diluted net loss per share attributable to Frontier common shareholders	$ (13.91)	$ (1.19)	$ (9.21)	$ (1.67)	$ (1.73)	$ (1.73)	$ (1.05)	$ (3.10)	$ (25.99)	$ (7.61)	$ (4.41)