Operating Segments (Details) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Operating segments
Number of operating segments | item													2
Revenue:
Lease rent revenue													$ 107,866	$ 101,748	$ 101,737
Maintenance reserve revenue													55,064	53,363	46,694
Spare parts sales													25,608	8,917
Gain on sale of leased equipment													8,354	5,753	5,675
Other revenue													2,718	4,506	4,306
Total revenue	$ 55,195	$ 57,758	$ 43,843	$ 42,814	$ 41,563	$ 45,519	$ 43,865	$ 43,340	$ 47,203	$ 37,952	$ 37,953	$ 35,304	199,610	174,287	158,412
Expenses:
Depreciation and amortization expense													69,586	65,441	58,727
Cost Of Spare Parts and Equipment Sales													17,866	7,474
General and administrative													42,744	35,859	33,868
Net finance costs													37,861	37,062
Other expense													18,584	17,938
Total expenses													186,641	163,774	150,638
Earnings from operations													12,969	10,513	$ 7,774
Total assets	1,308,577				1,261,626								1,308,577	1,261,626
Intersegment Eliminations [Member]
Revenue:
Other revenue													(458)	(736)
Total revenue													(458)	(736)
Expenses:
Earnings from operations													(458)	(736)
Leasing and Related Operations
Revenue:
Lease rent revenue														101,748
Maintenance reserve revenue														53,363
Gain on sale of leased equipment														5,753
Other revenue														3,581
Total revenue														164,445
Expenses:
Depreciation and amortization expense														65,152
General and administrative														33,211
Net finance costs														36,779
Other expense														17,830
Total expenses														152,972
Earnings from operations														11,473
Total assets	1,281,991				1,239,227								1,281,991	1,239,227
Leasing and Related Operations | Operating Segments [Member]
Revenue:
Lease rent revenue													107,866
Maintenance reserve revenue													55,064
Spare parts sales													9,975
Gain on sale of leased equipment													8,354
Other revenue													2,517
Total revenue													183,776
Expenses:
Depreciation and amortization expense													69,299
Cost Of Spare Parts and Equipment Sales													5,734
General and administrative													39,974
Net finance costs													37,474
Other expense													18,584
Total expenses													171,065
Earnings from operations													12,711
Spare Parts Sales
Revenue:
Spare parts sales														8,917
Other revenue														1,661
Total revenue														10,578
Expenses:
Depreciation and amortization expense														289
Cost Of Spare Parts and Equipment Sales														7,474
General and administrative														2,648
Net finance costs														283
Other expense														108
Total expenses														10,802
Earnings from operations														(224)
Total assets	$ 26,586				$ 22,399								26,586	$ 22,399
Spare Parts Sales | Operating Segments [Member]
Revenue:
Spare parts sales													15,633
Other revenue													659
Total revenue													16,292
Expenses:
Depreciation and amortization expense													287
Cost Of Spare Parts and Equipment Sales													12,132
General and administrative													2,770
Net finance costs													387
Total expenses													15,576
Earnings from operations													$ 716