Weighted-Average Actuarial Assumptions used to Determine Net Periodic Benefit Cost (Detail)	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Pension and Other Postretirement Benefits Disclosure [Line Items]
Expected long-term return on plan assets	4.20%	4.20%	4.00%
Rate of compensation increase	3.30%	4.20%	3.90%
Discount rate	3.20%	4.90%	4.10%