Pensions and Other Postretirement Benefits - Weighted Average Asset Allocations of Investment Portfolio for Pension Plans (Detail)	12 Months Ended
	Aug. 31, 2013	Aug. 31, 2012
U.S. Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	55.00%
Weighted average asset allocation	55.00%	56.00%
International Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	15.00%
Weighted average asset allocation	15.00%	15.00%
Fixed Income Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	25.00%
Weighted average asset allocation	25.00%	24.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	5.00%
Weighted average asset allocation	5.00%	5.00%