Segment Reporting - Segment Wide Reporting Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Nov. 30, 2012	Nov. 30, 2011
Segment Reporting Information [Line Items]
Sales	$ 118,022	$ 108,168
Income (loss) from operations	4,020	4,359
Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	90,368	82,244
Income (loss) from operations	1,387	743
Food Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	27,654	25,924
Income (loss) from operations	5,355	5,959
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(2,722)	(2,343)
Industrial Starch [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	43,802	32,386
Ethanol [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	23,403	32,436
By-Products [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	$ 23,163	$ 17,422