Sublease Table (Details) - B-717-200 Aircraft - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
B717 Sublease Liability [Line Items]
Sublease Obligations		$ 30	$ 63	$ 122
Interest Expense, Accretion		1	5
Additional Estimated Loss on Sublease		5	22
Sublease Transaction Costs	[1]	$ (39)	$ (86)

[1] Includes lease conversion cost payments