Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 3,466,248	$ 3,189,643
Accumulated depreciation	(1,368,992)	(1,249,867)
Property and equipment, net	2,097,256	1,939,776
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	125,900	222,400
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	3,116,838	2,856,142
Operating Leases, Future Minimum Payments Receivable, in Two Years	227,000	195,500
Operating Leases, Future Minimum Payments Receivable, in Three Years	182,500	150,500
Operating Leases, Future Minimum Payments Receivable, in Four Years	131,900	99,800
Operating Leases, Future Minimum Payments Receivable, in Five Years	118,800	90,700
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	64,245	65,857
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	38,309	36,193
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 246,856	$ 231,451