Information about Net Periodic Benefit Cost for Pension and Other Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Pension and Other Postretirement Benefits Disclosure [Line Items]
Service cost	$ 1,224	$ 1,494	$ 1,389
Interest cost	7,494	5,715	5,681
Expected long-term return on plan assets	(6,104)	(4,474)	(4,270)
Recognized actuarial loss	1,207	2,073	1,303
Net curtailment gain		(1,903)
Amortization of prior service cost	(26)	(27)	(115)
Net periodic benefit cost	$ 3,795	$ 2,878	$ 3,988