Fair Value Measurements and Derivative Instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Aug. 31, 2011	Aug. 31, 2013 Commodity Contract [Member]	Aug. 31, 2013 Commodity Contract [Member] Designated as Hedging Instrument [Member] Corn Futures [Member] bu	Aug. 31, 2013 Commodity Contract [Member] Firm Priced Starch and Ethanol Futures [Member] Designated as Hedging Instrument [Member] Corn Futures [Member] bu	Aug. 31, 2013 Commodity Contract [Member] Open Position [Member] Designated as Hedging Instrument [Member] Corn Futures [Member] bu	Aug. 31, 2013 Iowa Department of Economic Development Loans [Member]	Aug. 31, 2012 Iowa Department of Economic Development Loans [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Carrying value of debt						$ 1,233,000	$ 1,433,000
Fair value of debt						1,200,000
Pretax losses continued to be deferred in accumulated other comprehensive income	500,000
Deferred loss, net of tax, recorded in other comprehensive income		$ (900,000)
Purchased corn positions			3,100,000	2,200,000	900,000