Reportable Segments (Details) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Reportable Segments
Number of operating segments | item										2
Revenue:
Lease rent revenue										$ 175,609	$ 130,369	$ 119,895
Revenue										87,009	80,189	57,091
Spare parts and equipment sales										71,141	51,423	17,783
Gain on sale of leased equipment										6,944	4,929	3,482
Other revenue										7,644	7,930	9,023
Total revenue		$ 118,190	$ 80,958	$ 78,702	$ 70,497	$ 63,189	$ 65,861	$ 67,844	$ 77,946	348,347	274,840	207,274
Expenses:
Depreciation expense										76,814	66,023	66,280
Cost of spare parts and equipment sales										61,025	40,848	13,293
Write-down of equipment										10,651	24,930	9,514
General and administrative										72,021	55,737	47,780
Technical expense										11,142	9,729	6,993
Net finance costs										64,220	48,720	41,281
Total expenses										295,873	245,987	185,141
Earnings from operations										52,474	28,853	22,133
Total assets	[1]	1,934,943				1,603,431				1,934,943	1,603,431
Eliminations
Revenue:
Other revenue										(1,662)	(1,373)	(1,635)
Total revenue										(1,662)	(1,373)	(1,635)
Expenses:
Earnings from operations										(1,662)	(1,373)	(1,635)
Leasing and Related Operations | Operating Segments
Revenue:
Lease rent revenue										175,609	130,369	119,895
Revenue										87,009	80,189	57,091
Spare parts and equipment sales										30,122	22,285	3,335
Gain on sale of leased equipment										6,944	4,458	3,246
Other revenue										7,579	7,702	8,711
Total revenue										307,263	245,003	192,278
Expenses:
Depreciation expense										76,502	65,677	65,939
Cost of spare parts and equipment sales										28,290	17,344	2,394
Write-down of equipment										10,651	24,930	9,514
General and administrative										67,608	52,024	44,703
Technical expense										11,142	9,729	6,993
Net finance costs										64,220	48,720	40,813
Total expenses										258,413	218,424	170,356
Earnings from operations										48,850	26,579	21,922
Total assets		1,882,860				1,556,406				1,882,860	1,556,406
Spare Parts Sales | Operating Segments
Revenue:
Spare parts and equipment sales										41,019	29,138	14,448
Gain on sale of leased equipment											471	236
Other revenue										1,727	1,601	1,947
Total revenue										42,746	31,210	16,631
Expenses:
Depreciation expense										312	346	341
Cost of spare parts and equipment sales										32,735	23,504	10,899
General and administrative										4,413	3,713	3,077
Net finance costs												468
Total expenses										37,460	27,563	14,785
Earnings from operations										5,286	3,647	$ 1,846
Total assets		$ 52,083				$ 47,025				$ 52,083	$ 47,025

[1] Total assets at December 31, 2018 and December 31, 2017 include the following assets of variable interest entity’s (“VIE’s”) that can only be used to settle the liabilities of the VIE’s: Cash, $656 and $130; Restricted Cash $70,261 and $40,272, Equipment, $1,032,599 and $657,333; and Other, $1,075 and $20,090 respectively.