Leases (Details) (USD $)	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Operating Leased Assets [Line Items]
Total rental expense	$ 10,900,000	$ 10,800,000	$ 7,400,000
2013	5,326,000
2014	4,350,000
2015	2,828,000
2016	1,378,000
2017	1,273,000
2018 and thereafter	1,470,000
Total minimum rental commitments	$ 16,625,000