Accounts Receivable (Details) - USD ($)	3 Months Ended	12 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Aug. 01, 2020
Statement [Line Items]
Total accounts receivable	$ 134,058,000	$ 128,585,000
Less allowance for doubtful accounts	1,988,000	1,769,000
Accounts receivable, net	$ 132,070,000	$ 126,816,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Cumulative Effect, Period of Adoption, Adjustment
Statement [Line Items]
Less allowance for doubtful accounts			$ 215,000
Accounts Receivable | Customer Concentration Risk | U.S. government
Statement [Line Items]
Concentration risk, percentage	30.40%	31.00%
Accounts Receivable | Customer Concentration Risk | Verizon
Statement [Line Items]
Concentration risk, percentage	10.10%
Billed Receivables | Commercial and International Customers
Statement [Line Items]
Total accounts receivable	$ 64,461,000	$ 67,109,000
Billed Receivables | U.S. Government and Its Agencies
Statement [Line Items]
Total accounts receivable	37,345,000	32,870,000
Unbilled Receivables | Commercial and International Customers
Statement [Line Items]
Total accounts receivable	28,806,000	21,588,000
Unbilled Receivables | U.S. Government and Its Agencies
Statement [Line Items]
Total accounts receivable	$ 3,446,000	$ 7,018,000