Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 3,569,770	$ 3,189,643
Accumulated depreciation	(1,433,557)	(1,249,867)
Property and equipment, net	2,136,213	1,939,776
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	67,400	222,400
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	3,196,849	2,856,142
Operating Leases, Future Minimum Payments Receivable, in Two Years	240,100	195,500
Operating Leases, Future Minimum Payments Receivable, in Three Years	196,100	150,500
Operating Leases, Future Minimum Payments Receivable, in Four Years	145,500	99,800
Operating Leases, Future Minimum Payments Receivable, in Five Years	132,400	90,700
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	63,074	65,857
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	38,749	36,193
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 271,098	$ 231,451