Disclosures About Fair Value of Financial Instruments - Gain (Loss) Recognized in Income on Derivative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ 151		$ (1,227)	$ (3,944)		$ 3,845
Futures | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	(253)		(963)	801		3,134
Futures | Operating and Other Costs
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	553	[1]		553	[1]
Forwards | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	508		534	(966)		280
Swaps | Cost of Sales, Canola Oil and Meal
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (104)		$ (798)	$ (3,779)		$ 431

[1] Represents non-routine derivative trading activity.