Summary of Significant Accounting and Reporting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Net sales from firm fixed-price contracts as a percentage of consolidated U.S. government net sales	79.70%
Net sales from cost-reimbursable contracts as a percentage of consolidated U.S. government net sales	20.30%
Cash and cash equivalents	$ 154,500,000	$ 356,642,000	$ 367,894,000	$ 558,804,000
Research and development expenses reimbursed by customers	13,103,000	5,172,000	5,665,000
Measurement of uncertain tax position, percentage that likelihood of tax benefit being realized upon ultimate settlement must be greater than	50.00%
Amount invested in money market mutual funds disclosed at fair value.	$ 4,628,000	$ 50,182,000
Minimum [Member]
Machinery and equipment, estimated useful lives	3 years
Maximum [Member]
Machinery and equipment, estimated useful lives	8 years