Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 3,351	$ (4,067)	$ (116,531)	$ 713
Foreign currency forward contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	12,504	(4,168)	(40,172)	846
Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(9,153)	(21)	(76,359)	(119)
Fuel swaps | Fuel
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 0	$ 122	$ 0	$ (14)