Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives			$ (6,353)	$ (49,607)
Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (3,636)	$ (32,781)	(12,936)	(49,798)
Foreign currency forward contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(2,464)	(32,705)	(11,712)	(49,607)
Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (1,172)	$ (76)	$ (1,224)	$ (191)