Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($)	3 Months Ended
	Oct. 31, 2021	Oct. 31, 2020
Disaggregation of Revenue [Line Items]
Net sales	$ 116,759,000	$ 135,218,000
Point in time
Disaggregation of Revenue [Line Items]
Net sales	40,763,000	52,702,000
Over time
Disaggregation of Revenue [Line Items]
Net sales	75,996,000	82,516,000
Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	109,102,000	113,644,000
Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	7,657,000	21,574,000
U.S. government
Disaggregation of Revenue [Line Items]
Net sales	35,169,000	43,890,000
Domestic
Disaggregation of Revenue [Line Items]
Net sales	56,555,000	56,714,000
Total United States
Disaggregation of Revenue [Line Items]
Net sales	91,724,000	100,604,000
International
Disaggregation of Revenue [Line Items]
Net sales	25,035,000	34,614,000
Commercial Solutions
Disaggregation of Revenue [Line Items]
Net sales	78,934,000	81,802,000
Commercial Solutions | Point in time
Disaggregation of Revenue [Line Items]
Net sales	24,200,000	29,671,000
Commercial Solutions | Over time
Disaggregation of Revenue [Line Items]
Net sales	54,734,000	52,131,000
Commercial Solutions | Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	78,720,000	80,988,000
Commercial Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	214,000	814,000
Commercial Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Net sales	11,034,000	9,458,000
Commercial Solutions | Domestic
Disaggregation of Revenue [Line Items]
Net sales	51,220,000	49,300,000
Commercial Solutions | Total United States
Disaggregation of Revenue [Line Items]
Net sales	62,254,000	58,758,000
Commercial Solutions | International
Disaggregation of Revenue [Line Items]
Net sales	16,680,000	23,044,000
Government Solutions
Disaggregation of Revenue [Line Items]
Net sales	37,825,000	53,416,000
Government Solutions | Point in time
Disaggregation of Revenue [Line Items]
Net sales	16,563,000	23,031,000
Government Solutions | Over time
Disaggregation of Revenue [Line Items]
Net sales	21,262,000	30,385,000
Government Solutions | Firm fixed-price
Disaggregation of Revenue [Line Items]
Net sales	30,382,000	32,656,000
Government Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Net sales	7,443,000	20,760,000
Government Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Net sales	24,135,000	34,432,000
Government Solutions | Domestic
Disaggregation of Revenue [Line Items]
Net sales	5,335,000	7,414,000
Government Solutions | Total United States
Disaggregation of Revenue [Line Items]
Net sales	29,470,000	41,846,000
Government Solutions | International
Disaggregation of Revenue [Line Items]
Net sales	$ 8,355,000	$ 11,570,000