Other Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Principal components of other assets
Deferred income tax asset	$ 1,216	$ 912
Lease incentives and lease premiums, net of amortization of $63,070 and $47,304, respectively	100,743	99,079
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	16,817	11,707
Deposit Assets	19,050	39,948
Interest Rate Derivative Assets, at Fair Value	891	4,886
Financing Receivable, after Allowance for Credit Loss, Noncurrent	1,906	4,292
Operating Lease, Right-of-Use Asset	9,143	0
Other assets	35,936	53,537
Total other assets	185,702	214,361
Amortization of lease incentives and lease premiums	$ 63,070	$ 47,304