Summary of Significant Accounting and Reporting Policies (Narrative) (Details)	12 Months Ended
	Jul. 31, 2018 USD ($) operating_segment	Jul. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)	Jul. 31, 2015 USD ($)
Number of reportable segments | operating_segment	2
Net sales from firm fixed-price contracts as a percentage of consolidated U.S. government net sales	75.20%
Net sales from cost-reimbursable contracts as a percentage of consolidated U.S. government net sales	24.80%
Cash and cash equivalents	$ 43,484,000	$ 41,844,000	$ 66,805,000	$ 150,953,000
Research and development expenses reimbursed by customers	$ 16,924,000	$ 27,050,000	$ 17,432,000
Measurement of uncertain tax position, percentage that likelihood of tax benefit being realized upon ultimate settlement must be greater than	50.00%
Non-current portion of capital lease obligations, Blended interest rate	6.10%
Minimum
Machinery and equipment, estimated useful lives	3 years
Maximum
Machinery and equipment, estimated useful lives	8 years