Restructuring Charges (Summary of Restructuring Charges) (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 05, 2020 airplane	Sep. 30, 2020 USD ($) airplane	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) airplane	Sep. 30, 2019 USD ($)	Jun. 30, 2020 airplane
Restructuring Cost and Reserve [Line Items]
Number of airplanes held for sale (in airplanes) | airplane		2		2		2
Restructuring expenses		$ 4,982	$ 0	$ 46,379	$ 0
Subsequent Event
Restructuring Cost and Reserve [Line Items]
Number of airplanes sold (in airplanes) | airplane	1
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		2,635		22,502
Pension and termination benefit charges
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		0		10,913
Contract exit costs and other
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		$ 2,347		$ 12,964