Operating Segments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Operating segments
Number of operating segments | segment			2
Revenue:
Lease rent revenue	$ 31,270	$ 28,055	$ 88,727	$ 79,197
Maintenance reserve revenue	14,229	16,119	45,562	39,035
Spare parts sales	4,160	9,133	10,465	15,000
Gain on sale of leased equipment	180	3,804	3,430	7,666
Other revenue	1,622	619	3,614	1,978
Total revenue	51,461	57,730	151,798	142,876
Expenses:
Depreciation and amortization expense	16,628	17,102	49,235	52,390
Cost Of Spare Parts and Equipment Sales	3,066	5,919	7,785	10,219
General and administrative	12,257	11,742	34,694	30,826
Net finance costs	10,230	9,805	30,772	28,081
Other expense	3,409	9,068	10,837	16,416
Total expenses	45,590	53,636	133,323	137,932
Earnings from operations	5,871	4,094	18,475	4,944
Total assets	1,291,328		1,291,328		$ 1,294,285
Operating Segments [Member] | Leasing and Related Operations
Revenue:
Lease rent revenue	31,270	28,055	88,727	79,197
Maintenance reserve revenue	14,229	16,119	45,562	39,035
Spare parts sales	900	4,600	1,800	5,450
Gain on sale of leased equipment	180	3,804	3,430	7,666
Other revenue	1,487	597	3,392	1,796
Total revenue	48,066	53,175	142,911	133,144
Expenses:
Depreciation and amortization expense	16,541	17,035	48,981	52,179
Cost Of Spare Parts and Equipment Sales	640	2,461	1,288	3,081
General and administrative	11,500	10,948	32,438	28,751
Net finance costs	10,116	9,707	30,443	27,789
Other expense	2,934	9,068	10,362	16,416
Total expenses	41,731	49,219	123,512	128,216
Earnings from operations	6,335	3,956	19,399	4,928
Total assets	1,266,245		1,266,245		1,267,414
Operating Segments [Member] | Spare Parts Sales
Revenue:
Spare parts sales	3,260	4,533	8,665	9,550
Other revenue	786	135	1,734	531
Total revenue	4,046	4,668	10,399	10,081
Expenses:
Depreciation and amortization expense	87	67	254	211
Cost Of Spare Parts and Equipment Sales	2,426	3,458	6,497	7,138
General and administrative	757	794	2,256	2,075
Net finance costs	114	98	329	292
Other expense	475		475
Total expenses	3,859	4,417	9,811	9,716
Earnings from operations	187	251	588	365
Total assets	25,083		25,083		$ 26,871
Intersegment Eliminations [Member]
Revenue:
Other revenue	(651)	(113)	(1,512)	(349)
Total revenue	(651)	(113)	(1,512)	(349)
Expenses:
Earnings from operations	$ (651)	$ (113)	$ (1,512)	$ (349)