Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) engine aircraft	Dec. 31, 2017 USD ($) engine	Dec. 31, 2016 USD ($)	Jun. 03, 2014
Investments
Net book value of equipment held for operating lease	$ 1,673,135	$ 1,342,571
Ownership interest (as a percent)	50.00%
Investment in WMES joint ventures at beginning of the period	$ 50,641	45,406	$ 41,295
Investment			5,545
Earnings (losses) from joint venture	3,800	7,158	1,813
Deferred gain on engine sale		(939)	(1,212)
Distribution	(5,730)	(1,880)	(1,167)
Foreign Currency Translation Adjustment	(770)	(896)	(868)
Investment in WMES joint ventures at end of the period	47,941	50,641	45,406
Revenue	87,009	80,189	57,091
Other revenue	$ 7,644	7,930	9,023
WMES
Investments
Number of engines in lease portfolio | engine	32
Number of aircraft in lease portfolio | aircraft	1
Net book value of equipment held for operating lease	$ 234,800
Ownership interest (as a percent)	100.00%
Investment in WMES joint ventures at beginning of the period	$ 36,014	32,470	27,272
Investment			5,545
Earnings (losses) from joint venture	3,899	5,867	2,032
Deferred gain on engine sale		(443)	(1,212)
Distribution	(5,730)	(1,880)	(1,167)
Investment in WMES joint ventures at end of the period	$ 34,183	$ 36,014	32,470
Number of engines sold to third party | engine	2	2
Proceeds from sale of engine		$ 14,800
Consolidated Statements of Income
Revenue	$ 38,465	40,211	35,463
Expenses	30,934	28,754	31,669
WMES net income	7,531	11,457	3,794
Consolidated Balance Sheets
Total assets	274,744	246,309
Total liabilities	198,534	165,228
Total WMES net equity	76,210	81,081
WMES | Other Revenue [Member]
Investments
Revenue	$ 2,600	$ 2,400	$ 2,100
Type of Revenue [Extensible List]	us-gaap:AssetManagement1Member	us-gaap:AssetManagement1Member	us-gaap:AssetManagement1Member
CASC Willis
Investments
Number of engines in lease portfolio | engine	4
Net book value of equipment held for operating lease	$ 51,900
Investment in WMES joint ventures at beginning of the period	14,627	$ 12,936	$ 14,023
Earnings (losses) from joint venture	(99)	1,291	(219)
Deferred gain on engine sale		(496)
Foreign Currency Translation Adjustment	(770)	(896)	(868)
Investment in WMES joint ventures at end of the period	$ 13,758	$ 14,627	$ 12,936
Number of engines sold to third party | engine		1
Proceeds from sale of engine		$ 11,200
CASC Willis Engine Lease Company Limited
Investments
Ownership interest (as a percent)				50.00%