Fair Value Measurements -Nonrecurring Basis (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) engine aircraft	Dec. 31, 2016 USD ($) engine aircraft	Dec. 31, 2015 USD ($)
Assets at fair value and gains (losses) recorded
Equipment held for sale	$ 34,172,000	$ 30,710,000
Assets at fair value	1,100,000	$ 68,000
Number of engines | engine		393
Asset write-down	$ 24,930,000	$ 9,514,000	$ 9,181,000
Equipment
Assets at fair value and gains (losses) recorded
Asset write-down		$ 2,000,000
Engine Parts
Assets at fair value and gains (losses) recorded
Number of engines | engine	9	6
Number of engines for which impairment is recorded earlier due to part out and sale | engine		1
Additional write-down		$ 2,000,000
Engine and aircraft
Assets at fair value and gains (losses) recorded
Additional write down to reflect the estimated market value		$ 5,500,000
Aircrafts
Assets at fair value and gains (losses) recorded
Number of aircraft | aircraft	5	1
Asset write-down	$ 4,700,000
Nonrecurring
Assets at fair value and gains (losses) recorded
Equipment held for lease	23,255,000	$ 1,196,000
Equipment held for sale	39,261,000	8,976,000
Spare parts inventory	5,336,000	1,538,000
Assets at fair value	67,852,000	11,710,000
Total losses on equipment held for lease	(12,879,000)	(3,674,000)
Total losses on equipment held for sale	(8,708,000)	(5,365,000)
Total losses on spare parts inventory	(3,343,000)	(475,000)
Total losses on assets	(24,930,000)	(9,514,000)
Nonrecurring | Engine Parts
Assets at fair value and gains (losses) recorded
Asset write-down	16,900,000
Nonrecurring | Level 2
Assets at fair value and gains (losses) recorded
Equipment held for lease	23,255,000	1,196,000
Equipment held for sale	39,261,000	8,976,000
Spare parts inventory	5,336,000	1,538,000
Assets at fair value	$ 67,852,000	$ 11,710,000
Engines and related equipment
Assets at fair value and gains (losses) recorded
Number of engines | engine	48