Fair Value Measurements and Derivative Instruments - Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 13,812	$ 14,455
Other expense
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	13,752	14,477
Foreign currency forward contracts | Other expense
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	13,812	14,455
Fuel swaps | Other expense
Derivative Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (60)	$ 22