Customer and Geographic Information (Details) (USD $)	12 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Revenue from External Customers [Line Items]
International sales, including sales to U.S. domestic companies for inclusion in products sold to international customers	$ 160,217,000	$ 164,503,000	$ 184,848,000
Minimum percentage of consolidated net sales sold to one customer or individual country requiring additional and separate disclosure	10.00%	10.00%	10.00%
U S Government [Member]
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type	34.70%	48.90%	61.70%
Commercial (United States) [Member]
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type	15.20%	12.40%	8.10%
Total United States Sales [Member]
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type	49.90%	61.30%	69.80%
International Sales [Member]
Revenue from External Customers [Line Items]
Percentage of revenue generated from external customer type	50.10%	38.70%	30.20%