Property and Equipment (Schedule of Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,290,329	$ 1,203,401
Accumulated depreciation	(452,157)	(384,477)
Property and equipment, net	838,172	818,924
Aircraft and flight equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,236,225	1,148,781
Support equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	51,179	52,209
Vehicles and other equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,771	1,597
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,154	$ 814