Investment in Other Companies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) engine	Dec. 31, 2018 USD ($)
Number of spare engines purchased | engine	14
Long-term debt	$ 2,984,818	$ 3,159,974
Aero Engines, LLC.
Payments to Acquire Interest in Joint Venture	$ 22,300
Investment ownership (as a percent)	75.00%
Number of spare engines sold to Aero Engines | engine	14
Long-term debt	$ 0
Investment balance in Aero Engines	22,600
Company's portion of income generated by Aero Engines	$ 300