Accounts Receivable (Details) - USD ($)	3 Months Ended	12 Months Ended
	Oct. 31, 2021	Jul. 31, 2021
Statement [Line Items]
Total accounts receivable	$ 138,289,000	$ 159,758,000
Less allowance for doubtful accounts	1,467,000	1,648,000
Accounts receivable, net	$ 136,822,000	$ 158,110,000
Accounts Receivable | Customer Concentration Risk | U.S. government
Statement [Line Items]
Concentration risk, percentage	23.00%	23.00%
Accounts Receivable | Customer Concentration Risk | AT&T, Inc.
Statement [Line Items]
Concentration risk, percentage	14.80%	12.70%
Accounts Receivable | Customer Concentration Risk | Verizon
Statement [Line Items]
Concentration risk, percentage	12.80%	12.10%
Billed Receivables | Commercial and International Customers
Statement [Line Items]
Total accounts receivable	$ 72,311,000	$ 86,890,000
Billed Receivables | U.S. Government and Its Agencies
Statement [Line Items]
Total accounts receivable	28,758,000	33,381,000
Unbilled Receivables | Commercial and International Customers
Statement [Line Items]
Total accounts receivable	34,210,000	36,131,000
Unbilled Receivables | U.S. Government and Its Agencies
Statement [Line Items]
Total accounts receivable	$ 3,010,000	$ 3,356,000