Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 1,812,366	$ 1,731,983
Accumulated depreciation	(754,489)	(730,991)
Property and equipment, net	1,057,877	1,000,992
Flight Equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	1,546,545	1,541,872
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	49,348	49,229
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	28,081	27,364
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 188,392	$ 113,518