Property and Equipment (Schedule of Property and Equipment) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,300,548	$ 1,290,329
Accumulated depreciation	(490,738)	(452,157)
Property and equipment, net	809,810	838,172
Aircraft and flight equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,247,913	1,236,225
Support equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	49,733	51,179
Vehicles and other equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,759	1,771
Leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,143	$ 1,154