Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (28,083)	$ 1,890
Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(28,212)	659
Foreign exchange contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	(28,083)	1,881
Fuel swaps | Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (129)	$ (1,222)