Stock-based Compensation Plans - Additional Information (Detail) (USD $)	12 Months Ended	1 Months Ended	12 Months Ended							1 Months Ended		12 Months Ended				1 Months Ended	2 Months Ended	12 Months Ended
	Aug. 31, 2012	Jan. 11, 2012 Carolina Starches, LLC [Member]	Aug. 31, 2012 Stock Options [Member]	Aug. 31, 2011 Stock Options [Member]	Aug. 31, 2010 Stock Options [Member]	Aug. 31, 2012 Restricted Stock [Member]	Aug. 31, 2011 Restricted Stock [Member]	Aug. 31, 2010 Restricted Stock [Member]	Jan. 26, 2010 Restricted Stock [Member]	Jan. 26, 2012 2006 Incentive Plan [Member]	Aug. 31, 2012 2006 Incentive Plan [Member]	Aug. 31, 2012 2006 Incentive Plan [Member] Stock Options [Member]	Aug. 31, 2011 2006 Incentive Plan [Member] Stock Options [Member]	Aug. 31, 2011 2006 Incentive Plan [Member] Stock Options [Member] Vesting Period One Year [Member]	Aug. 31, 2011 2006 Incentive Plan [Member] Stock Options [Member] Vesting Period Four Years [Member]	Jan. 01, 2010 2006 Incentive Plan [Member] Restricted Stock [Member] Non Employee Directors [Member]	Jan. 26, 2010 2006 Incentive Plan [Member] Restricted Stock [Member] Non Employee Directors [Member]	Aug. 31, 2012 2006 Incentive Plan [Member] Non Qualified Stock Options And Restricted Stock [Member]	Aug. 31, 2012 2006 Incentive Plan [Member] Non Qualified Stock Options And Restricted Stock [Member] Minimum [Member]	Aug. 31, 2012 2006 Incentive Plan [Member] Non Qualified Stock Options And Restricted Stock [Member] Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional common shares authorized for issuance under the plan (in shares)										800,000
Number of common shares available for issuance under the plan (in shares)											353,616
Vesting period (in Years)		2 years										3 years		1 year	4 years	1 year	1 year		1 year	4 years
Expiration period (in years)																		P7Y
Share price of Company's stock (in USD per share)	$ 7.31
Options granted during the period		82,500										678,000	98,000	80,000	18,000
Option term		7 years
Compensation expense related to non-vested awards not yet recognized			$ 1,500,000
Weighted-average period over which unrecognized compensation cost will be recognized (in years)			1 year 4 months 24 days			4 months 24 days
Stock options exercised (in shares)	0		1.5	0.0	0.0
Weighted-Average Grant-Date Fair Value, Granted (in USD per share)						$ 5.65		$ 6.60
Restricted stock awards granted (in shares)						100,000			3,539
Total fair value of restricted stock vested						$ 1,000,000	$ 1,200,000	$ 1,000,000
Number of shares issued for non-employee director (in shares)																2,301