Property and Equipment (Schedule of Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 3,189,643	$ 2,912,217
Accumulated depreciation	(1,249,867)	(1,146,197)
Property and equipment, net	1,939,776	1,766,020
Flight Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	222,400
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	2,856,142	2,598,113
Operating Leases, Future Minimum Payments Receivable, in Two Years	195,500
Operating Leases, Future Minimum Payments Receivable, in Three Years	150,500
Operating Leases, Future Minimum Payments Receivable, in Four Years	99,800
Operating Leases, Future Minimum Payments Receivable, in Five Years	90,700
Ground equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	65,857	59,628
facilities, leasehold improvements and office equipment [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	36,193	33,649
Construction in Progress [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Property and equipment, gross	$ 231,451	$ 220,827