Customer and Geographic Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2012	Apr. 30, 2011
International sales including sales to domestic companies for inclusion in products sold to international customers	$ 39,653,000	$ 52,706,000	$ 124,621,000	$ 137,024,000
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	48.60%	49.00%	47.80%	63.00%
Commercial (United States) [Member]
Percentage of revenue generated from external customer type	11.70%	10.80%	12.30%	8.00%
Total United States Sales [Member]
Percentage of revenue generated from external customer type	60.30%	59.80%	60.10%	71.00%
International Sales [Member]
Percentage of revenue generated from external customer type	39.70%	40.20%	39.90%	29.00%