Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,415,873	$ 1,363,435
Accumulated depreciation	(556,391)	(516,167)
Property and equipment, net	859,482	847,268
Flight Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,335,943	1,285,966
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	33,735	33,677
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	25,152	25,180
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 21,043	$ 18,612