Consolidated Statements of Income - USD ($) shares in Thousands, $ 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
Depreciation and amortization 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:
Interest expense									64,220	48,720	41,144
Loss on debt extinguishment											137
Total 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 expense (benefit)									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
Basic weighted average earnings per common share (in dollars per share)	$ 2.99	$ 1.50	$ 1.28	$ 1.03	$ 6.87	$ 0.82	$ 0.94	$ 1.28	$ 6.75	$ 9.93	$ 2.10
Diluted weighted average earnings per common share (in dollars per share)	$ 2.91	$ 1.47	$ 1.26	$ 1.00	$ 6.75	$ 0.80	$ 0.92	$ 1.25	$ 6.60	$ 9.69	$ 2.05
Basic weighted average common shares outstanding (in shares)	5,782	5,900	5,878	6,104	6,090	6,055	6,036	6,114	5,915	6,074	6,570
Diluted weighted average common shares outstanding (in shares)	5,939	6,004	5,991	6,256	6,201	6,184	6,158	6,240	6,046	6,220	6,714