Derivative Financial Instruments (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 0	$ 0
Derivatives not designated as hedging instruments
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	3,669	15,486
Derivatives not designated as hedging instruments | Product contracts | Maximum
Derivative Financial Instruments
Nonmonetary units	250,000
Derivatives not designated as hedging instruments | Product contracts | Cost of sales
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	3,651	15,543
Derivatives not designated as hedging instruments | Foreign currency derivatives | Cost of sales
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 18	$ (57)