Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives			$ (24,234)	$ (8,634)
Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(35,395)	16,971	(25,562)	(10,224)
Foreign exchange contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(35,175)	16,789	(24,405)	(10,491)
Fuel swaps | Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(220)	220	(1,157)	268
Fuel swaps | Options | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 0	$ (38)	$ 0	$ (1)