SCHEDULE I - Parent Company Information - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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
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
Interest expense									64,220	48,720	41,144
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
Earnings from joint ventures									3,800	7,158	1,813
Income before income taxes									56,274	36,011	23,946
Income tax (benefit) expense									(13,043)	26,147	(9,877)
Net income									43,231	62,158	14,069
Preferred stock dividends									3,250	1,813	281
Accretion of preferred stock issuance costs									83	46	8
Net income attributable to common shareholders	$ 17,274	$ 8,834	$ 7,528	$ 6,261	$ 41,864	$ 4,939	$ 5,657	$ 7,839	39,898	60,299	13,780
Parent Company [Member]
REVENUE
Lease rent revenue									70,269	72,580	76,283
Revenue									27,407	46,163	30,742
Spare parts and equipment sales									35,388	35,903	8,404
Gain on sale of leased equipment									6,183	3,696	3,322
Other revenue									13,624	9,881	10,660
Total revenue									152,871	168,223	129,411
EXPENSES
Depreciation and amortization expense									34,795	40,560	43,451
Cost of spare parts and equipment sales									32,331	29,705	6,591
Write-down of equipment									2,567	17,881	5,989
General and administrative									52,896	42,004	39,201
Technical expense									9,858	7,058	4,637
Net finance costs									25,210	25,215	23,358
Total expenses									157,657	162,423	123,227
Earnings from operations									(4,786)	5,800	6,184
Earnings from joint ventures									3,800	7,158	1,813
Income before income taxes									(986)	12,958	7,997
Income tax (benefit) expense									(280)	4,843	4,710
Equity in income of subsidiaries, net of tax of $13,323, $(30,990), and $5,168 at December 31, 2018, 2017 and 2016, respectively									43,937	54,043	10,782
Net income									43,231	62,158	14,069
Preferred stock dividends									3,250	1,813	281
Accretion of preferred stock issuance costs									83	46	8
Net income attributable to common shareholders									$ 39,898	$ 60,299	$ 13,780