Property and Equipment (Schedule of Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,292,537	$ 1,290,329
Accumulated depreciation	(475,096)	(452,157)
Property and equipment, net	817,441	838,172
Aircraft and flight equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,238,297	1,236,225
Support equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	51,319	51,179
Vehicles and other equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,787	1,771
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,134	$ 1,154