Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,450,049	$ 1,363,435
Accumulated depreciation	(581,152)	(516,167)
Property and equipment, net	868,897	847,268
Flight Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,337,091	1,285,966
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	34,675	33,677
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	25,171	25,180
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 53,112	$ 18,612