Disclosures About Fair Value of Financial Instruments - Gain (Loss) Recognized in Income on Derivative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ 526	$ 6,327	$ (3,418)	$ (2,482)
Futures | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	99	5,592	900	(2,458)
Futures | Operating and Other Costs
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	1,397		1,950
Forwards | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	488	(49)	(478)	329
Swaps | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (61)	$ 784	$ (3,840)	$ (353)