Customer and Geographic Information (Details) (USD $)	3 Months Ended
	Oct. 31, 2012	Oct. 31, 2011
International sales, including sales to U.S. domestic companies for inclusion in products sold to international customers	$ 39,217,000	$ 43,978,000
Minimum percentage of consolidated net sales sold to one customer or individual country requiring additional and separate disclosure	10.00%	10.00%
U S Government [Member]
Percentage of revenue generated from external customer type	43.40%	48.30%
Commercial (United States) [Member]
Percentage of revenue generated from external customer type	13.50%	12.90%
Total United States Sales [Member]
Percentage of revenue generated from external customer type	56.90%	61.20%
International Sales [Member]
Percentage of revenue generated from external customer type	43.10%	38.80%