Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives			$ (49,607)	$ (24,234)
Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (32,781)	$ (35,395)	(49,798)	(25,562)
Foreign exchange contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(32,705)	(35,175)	(49,607)	(24,405)
Fuel swaps | Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (76)	$ (220)	$ (191)	$ (1,157)