Operating Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Operating segments
Number of operating segments | segment			2
Revenue:
Lease rent revenue	$ 29,181	$ 25,882	$ 57,457	$ 51,142
Maintenance reserve revenue	15,514	10,477	31,333	22,916
Spare parts sales	3,673	3,716	6,305	5,867
Gain on sale of leased equipment	258	3,132	3,250	3,862
Other revenue	992	603	1,992	1,359
Total revenue	49,618	43,810	100,337	85,146
Expenses:
Depreciation and amortization expense	16,188	17,626	32,607	35,288
Cost Of Spare Parts and Equipment Sales	2,787	2,820	4,719	4,300
General and administrative	10,685	9,112	22,437	19,084
Net finance costs	10,534	9,860	20,542	18,276
Other expense	3,696	5,492	7,428	7,348
Total expenses	43,890	44,910	87,733	84,296
Earnings (loss) from operations	5,728	(1,100)	12,604	850
Total assets	1,292,397		1,292,397		$ 1,294,285
Operating Segments [Member] | Leasing and Related Operations
Revenue:
Lease rent revenue	29,181	25,882	57,457	51,142
Maintenance reserve revenue	15,514	10,477	31,333	22,916
Spare parts sales	900	850	900	850
Gain on sale of leased equipment	258	3,132	3,250	3,862
Other revenue	972	583	1,905	1,199
Total revenue	46,825	40,924	94,845	79,969
Expenses:
Depreciation and amortization expense	16,103	17,554	32,440	35,144
Cost Of Spare Parts and Equipment Sales	648	620	648	620
General and administrative	9,958	8,390	20,938	17,729
Net finance costs	10,414	9,756	20,327	18,082
Other expense	3,696	5,492	7,428	7,348
Total expenses	40,819	41,812	81,781	78,923
Earnings (loss) from operations	6,006	(888)	13,064	1,046
Total assets	1,267,186		1,267,186		1,267,414
Operating Segments [Member] | Spare Parts Sales
Revenue:
Spare parts sales	2,773	2,866	5,405	5,017
Other revenue	590	100	948	396
Total revenue	3,363	2,966	6,353	5,413
Expenses:
Depreciation and amortization expense	85	72	167	144
Cost Of Spare Parts and Equipment Sales	2,139	2,200	4,071	3,680
General and administrative	727	722	1,499	1,355
Net finance costs	120	104	215	194
Total expenses	3,071	3,098	5,952	5,373
Earnings (loss) from operations	292	(132)	401	40
Total assets	25,211		25,211		$ 26,871
Intersegment Eliminations [Member]
Revenue:
Other revenue	(570)	(80)	(861)	(236)
Total revenue	(570)	(80)	(861)	(236)
Expenses:
Earnings (loss) from operations	$ (570)	$ (80)	$ (861)	$ (236)