Segment Reporting - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2013 Segment	Aug. 31, 2012	Aug. 31, 2011
Segment Reporting Information [Line Items]
Number of segments									2
Sales	$ 117,427	$ 121,719	$ 110,082	$ 118,022	$ 110,223	$ 111,283	$ 103,477	$ 108,168	$ 467,250	$ 433,151	$ 373,763
Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales									356,016	330,607	291,523
Carolina Starches, LLC [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales									$ 26,900