Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,077	$ 1,064	$ 982
Interest cost	576	523	392
Expected return on plan assets	(651)	(568)	(429)
Amortization of transition asset obligations	(26)	(28)	(25)
Amortization of prior service costs	10	10	9
Amortization of net actuarial loss recognized	210	184	174
Total cost	$ 1,196	$ 1,185	$ 1,103