Customer and Geographic Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
International sales, including sales to U.S. domestic companies for inclusion in products sold to international customers	$ 40,471,000	$ 40,990,000	$ 79,689,000	$ 84,968,000
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]
Percentage of revenue generated from external customer type	32.80%	46.50%	38.60%	47.50%
Commercial (United States) [Member]
Percentage of revenue generated from external customer type	12.90%	12.10%	13.30%	12.50%
Total United States Sales [Member]
Percentage of revenue generated from external customer type	45.70%	58.60%	51.90%	60.00%
International Sales [Member]
Percentage of revenue generated from external customer type	54.30%	41.40%	48.10%	40.00%