Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($)	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 135,218,000	$ 170,267,000
Point in time
Disaggregation of Revenue [Line Items]
Net sales	52,702,000	75,509,000
Over time
Disaggregation of Revenue [Line Items]
Net sales	82,516,000	94,758,000
Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	113,644,000	143,272,000
Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	21,574,000	26,995,000
U.S. government
Disaggregation of Revenue [Line Items]
Net sales	43,890,000	69,521,000
Domestic
Disaggregation of Revenue [Line Items]
Net sales	56,714,000	61,395,000
Total United States
Disaggregation of Revenue [Line Items]
Net sales	100,604,000	130,916,000
International
Disaggregation of Revenue [Line Items]
Net sales	34,614,000	39,351,000
Commercial Solutions
Disaggregation of Revenue [Line Items]
Net sales	81,802,000	94,314,000
Commercial Solutions | Point in time
Disaggregation of Revenue [Line Items]
Net sales	29,671,000	37,723,000
Commercial Solutions | Over time
Disaggregation of Revenue [Line Items]
Net sales	52,131,000	56,591,000
Commercial Solutions | Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	80,988,000	92,548,000
Commercial Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	814,000	1,766,000
Commercial Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Net sales	9,458,000	16,748,000
Commercial Solutions | Domestic
Disaggregation of Revenue [Line Items]
Net sales	49,300,000	53,354,000
Commercial Solutions | Total United States
Disaggregation of Revenue [Line Items]
Net sales	58,758,000	70,102,000
Commercial Solutions | International
Disaggregation of Revenue [Line Items]
Net sales	23,044,000	24,212,000
Government Solutions
Disaggregation of Revenue [Line Items]
Net sales	53,416,000	75,953,000
Government Solutions | Point in time
Disaggregation of Revenue [Line Items]
Net sales	23,031,000	37,786,000
Government Solutions | Over time
Disaggregation of Revenue [Line Items]
Net sales	30,385,000	38,167,000
Government Solutions | Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	32,656,000	50,724,000
Government Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	20,760,000	25,229,000
Government Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Net sales	34,432,000	52,773,000
Government Solutions | Domestic
Disaggregation of Revenue [Line Items]
Net sales	7,414,000	8,041,000
Government Solutions | Total United States
Disaggregation of Revenue [Line Items]
Net sales	41,846,000	60,814,000
Government Solutions | International
Disaggregation of Revenue [Line Items]
Net sales	$ 11,570,000	$ 15,139,000