Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Principal components of other assets
Deferred income tax asset	$ 1,736	$ 1,902
Lease incentives and lease premiums, net of amortization of $38,827 and $39,638, respectively	69,721	96,587
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment	3,627	3,834
Deposit Assets	28,541	12,923
Interest Rate Derivative Assets, at Fair Value	2,663	5,735
Other assets	25,107	27,417
Total other assets	131,395	148,398
Amortization of lease incentives and lease premiums	$ 38,827	$ 39,638