Sales, Attributed to Area to Which Product was Shipped (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Sales Concentration [Line Items]
Sales	$ 361,363	$ 315,441	$ 254,274
United States [Member]
Sales Concentration [Line Items]
Sales	328,282	288,571	231,042
Canada [Member]
Sales Concentration [Line Items]
Sales	5,653	4,027	3,738
Mexico [Member]
Sales Concentration [Line Items]
Sales	12,761	9,221	6,996
Columbia [Member]
Sales Concentration [Line Items]
Sales	6,678	6,802	6,227
Japan [Member]
Sales Concentration [Line Items]
Sales	4,380	3,434	1,173
Other Country [Member]
Sales Concentration [Line Items]
Sales	3,609	3,386	5,098
Non-United States [Member]
Sales Concentration [Line Items]
Sales	$ 33,081	$ 26,870	$ 23,232