Derivative Financial Instruments - Not Designated (Details) - Derivatives not designated as hedging instruments $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) item	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) item	Jun. 30, 2015 USD ($)
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 390	$ 877	$ 14	$ 4,545
Commodity product | Cost of sales
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 326	863	$ (89)	4,513
Commodity product | Maximum
Derivative Financial Instruments
Aggregate units of products in a controlled trading program | item	250,000		250,000
Foreign Exchange | Cost of sales
Derivative Financial Instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ 64	$ 14	$ 103	$ 32