Customer and Geographic Information (Details) (USD $)	3 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
International sales including sales to domestic companies for inclusion in products sold to international customers	$ 43,978,000	$ 36,064,000
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	48.30%	73.60%
Commercial (United States) [Member]
Percentage of revenue generated from external customer type	12.90%	6.20%
Total United States Sales [Member]
Percentage of revenue generated from external customer type	61.20%	79.80%
International Sales [Member]
Percentage of revenue generated from external customer type	38.80%	20.20%