Fair Value Measurements - Nonrecurring Basis (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($) engine	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($) engine	Dec. 31, 2017 USD ($)
Assets at fair value and gains (losses) recorded
Equipment held for sale	$ 18,430		$ 18,430		$ 34,172
Assets at fair value	2,500		2,500		1,100
Increase (decrease) in asset write-down			3,600
Asset write-down	3,578	$ 1,351	3,578	$ 13,442
Engine Parts
Assets at fair value and gains (losses) recorded
Number of engines | engine		4		4
Engine and aircraft
Assets at fair value and gains (losses) recorded
Asset write-down				$ 13,400
Nonrecurring
Assets at fair value and gains (losses) recorded
Equipment held for lease					23,255
Equipment held for sale	3,227		3,227		39,261
Spare parts inventory	593		593		5,336
Assets at fair value	3,820		3,820		67,852
Total losses on equipment held for lease				(9,019)
Total losses on equipment held for sale			(3,578)	(4,423)
Total losses on spare parts inventory			(1,517)	(1,843)
Total losses on assets			(5,095)	$ (15,285)
Nonrecurring | Level 2
Assets at fair value and gains (losses) recorded
Equipment held for lease					23,255
Equipment held for sale	3,227		3,227		39,261
Spare parts inventory	593		593		5,336
Assets at fair value	$ 3,820		$ 3,820		$ 67,852