Segment Reporting (Restated) - Segment Wide Reporting Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Segment Reporting Information [Line Items]
Sales	$ 110,082	$ 103,477	$ 228,104	$ 211,645
Income (loss) from operations	2,530	1,650	6,550	6,009
Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	83,478	78,573	173,846	160,817
Income (loss) from operations	(452)	(985)	935	(242)
Food Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	26,604	24,904	54,258	50,828
Income (loss) from operations	5,535	5,247	10,891	11,206
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(2,553)	(2,612)	(5,276)	(4,955)
Industrial Starch [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	44,237	37,052	88,039	69,438
Ethanol [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	18,196	24,232	41,599	56,668
By-Products [Member] | Industrial Ingredients [Member]
Segment Reporting Information [Line Items]
Sales	$ 21,045	$ 17,289	$ 44,208	$ 34,711