SCHEDULE I - Parent Company Information - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUE
Lease rent revenue													$ 130,369	$ 119,895	$ 108,046
Maintenance reserve revenue													80,189	57,091	53,396
Spare parts and equipment sales													51,423	17,783	25,582
Gain on sale of leased equipment													4,929	3,482	8,320
Other revenue													7,930	9,023	2,718
Total revenue	$ 63,189	$ 65,861	$ 67,844	$ 77,946	$ 55,476	$ 51,461	$ 49,618	$ 50,719	$ 55,186	$ 57,730	$ 43,810	$ 41,336	274,840	207,274	198,062
EXPENSES
Cost Of Spare Parts and Equipment Sales													40,848	13,293	17,849
Write-down of equipment													24,930	9,514	9,181
General and administrative													55,737	47,780	42,744
Technical expense													9,729	6,993	9,403
Interest expense													48,720	41,144	39,012
Total expenses													245,987	185,141	186,462
Earnings from operations													28,853	22,133	11,600
Earnings from joint ventures													7,158	1,813	1,175
Income before income taxes													36,011	23,946	12,775
Income tax (benefit) expense													26,147	(9,877)	(6,315)
Net income													62,158	14,069	6,460
Preferred stock dividends													1,813	281
Accretion of preferred stock issuance costs													46	8
Net income attributable to common shareholders	$ 41,864	$ 4,939	$ 5,657	$ 7,839	$ 2,418	$ 3,985	$ 3,366	$ 4,011	$ 3,037	$ 2,551	$ (486)	$ 1,358	60,299	13,780	6,460
Parent Company
REVENUE
Lease rent revenue													72,580	76,283	63,443
Maintenance reserve revenue													46,163	30,742	29,937
Spare parts and equipment sales													35,903	8,404	20,210
Gain on sale of leased equipment													3,696	3,322	2,420
Other revenue													9,881	10,660	7,017
Total revenue													168,223	129,411	123,027
EXPENSES
Depreciation expense													40,560	43,451	40,623
Cost Of Spare Parts and Equipment Sales													29,705	6,591	13,559
Write-down of equipment													17,881	5,989	6,764
General and administrative													42,004	39,201	35,898
Technical expense													7,058	4,637	6,805
Interest expense													25,215	23,358	18,448
Total expenses													162,423	123,227	122,097
Earnings from operations													5,800	6,184	930
Earnings from joint ventures													7,158	1,813	1,175
Income before income taxes													12,958	7,997	2,105
Income tax (benefit) expense													4,843	4,710	2,277
Equity in income of subsidiaries, net of tax of $30,990, $5,168, and $4,037 at December 31, 2017, 2016 and 2015, respectively													54,043	10,782	6,632
Net income													62,158	14,069	6,460
Preferred stock dividends													1,813	281
Accretion of preferred stock issuance costs													46	8
Net income attributable to common shareholders													$ 60,299	$ 13,780	$ 6,460