Customer and Geographic Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013	Apr. 30, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
International sales, including sales to U.S. domestic companies for inclusion in products sold to international customers	$ 32,907,000	$ 39,653,000	$ 112,596,000	$ 124,621,000
Minimum percentage of consolidated net sales sold to one customer or individual country requiring additional and separate disclosure	10.00%	10.00%	10.00%	10.00%
U S Government [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue generated from external customer type	36.90%	48.60%	38.10%	47.80%
Commercial (United States) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue generated from external customer type	16.00%	11.70%	14.10%	12.30%
Total United States Sales [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue generated from external customer type	52.90%	60.30%	52.20%	60.10%
International Sales [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Percentage of revenue generated from external customer type	47.10%	39.70%	47.80%	39.90%