Customer and Geographic Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011
International sales including sales to domestic companies for inclusion in products sold to international customers	$ 40,990,000	$ 48,254,000	$ 84,968,000	$ 84,318,000
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	46.50%	62.70%	47.50%	68.30%
Commercial (United States) [Member]
Percentage of revenue generated from external customer type	12.10%	7.70%	12.50%	7.00%
Total United States Sales [Member]
Percentage of revenue generated from external customer type	58.60%	70.40%	60.00%	75.30%
International Sales [Member]
Percentage of revenue generated from external customer type	41.40%	29.60%	40.00%	24.70%