Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 14,455	$ (28,083)
Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	14,477	(28,212)
Foreign exchange contracts | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	14,455	(28,083)
Fuel swaps | Fuel swaps | Other income (expense)
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 22	$ (129)