Employee Benefit Plans (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Schedule of Net Periodic Benefit Costs
Service cost - benefits attributed to service during the period	$ 666	$ 662	$ 672
Prior service cost	(82)	(64)	(70)
Interest cost on accumulated postretirement benefit obligation	694	795	842
Amortization of unrecognized gain	(76)	(206)	(308)
Curtailment loss			393
Periodic postretirement benefit cost	$ 1,202	$ 1,187	$ 1,529
Schedule of Assumptions Used
Weighted average discount rate used in determining accumulated postretirement benefit obligation liability	4.50%	4.50%	5.50%
Weighted average discount rate used in determining net periodic benefit cost	4.50%	5.50%	6.80%
Assumed health care trend rate used to measure APBO at July 31	8.00%	8.00%	8.00%
Rate to which cost trend rate is assumed to decline (the ultimate trend rate)	5.50%	5.50%	5.50%
Fiscal year the ultimate trend rate is reached	2017	2016	2015