Net Periodic Benefit Cost for Pension Plans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2013	May 31, 2012
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 492	$ 370	$ 1,518	$ 1,060
Interest cost	1,848	1,986	5,686	5,609
Expected long-term return on plan assets	(1,667)	(1,650)	(5,136)	(4,524)
Amortization of prior service cost	(6)	(7)	(19)	(21)
Recognized actuarial loss	670	308	2,037	913
Net periodic benefit cost	$ 1,337	$ 1,007	$ 4,086	$ 3,037