Property and Equipment (Schedule of Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,398,180	$ 1,363,435
Accumulated depreciation	(540,730)	(516,167)
Property and equipment, net	857,450	847,268
Flight Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,325,289	1,285,966
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	33,660	33,677
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	25,148	25,180
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 14,083	$ 18,612