Acquisitions (Fair Value of Assets Acquired and Liabilities Assumed) (Details) - USD ($)			3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2020	Jan. 27, 2020	Apr. 30, 2020	Apr. 30, 2020	Jul. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 335,477,000		$ 335,477,000	$ 335,477,000	$ 310,489,000
Customer relationships
Measurement Period Adjustments
Estimated useful lives				20 years 5 months	20 years 6 months
CGC Technology
Business Acquisition [Line Items]
Settled or payable in cash	12,075,000	$ 12,075,000
Settled or payable in common stock issued by Comtech	11,575,000	11,575,000
Preliminary purchase price at fair value	23,650,000	23,650,000
Cash and cash equivalents	160,000	160,000	160,000	$ 160,000
Current assets	4,390,000	3,336,000	4,390,000	4,390,000
Property, plant and equipment	1,457,000	1,457,000	1,457,000	1,457,000
Operating lease assets	924,000	924,000	924,000	924,000
Deferred tax assets, non-current	1,075,000	588,000	1,075,000	1,075,000
Contract liabilities	(6,890,000)	0	(6,890,000)	(6,890,000)
Accrued warranty obligations	(1,000,000)	(1,000,000)	(1,000,000)	(1,000,000)
Other current liabilities	(6,198,000)	(7,060,000)	(6,198,000)	(6,198,000)
Non-current liabilities	(1,329,000)	(1,329,000)	(1,329,000)	(1,329,000)
Net tangible liabilities at preliminary fair value	(7,411,000)	(2,924,000)	(7,411,000)	(7,411,000)
Deferred tax liabilities	(2,091,000)	(2,176,000)	(2,091,000)	(2,091,000)
Goodwill	20,852,000	15,950,000	20,852,000	20,852,000
Allocation of aggregate purchase price	23,650,000	23,650,000	23,650,000	23,650,000
Measurement Period Adjustments
Current assets			1,054,000
Deferred tax assets, non-current			487,000
Contract liabilities			(6,890,000)
Other current liabilities			862,000
Net tangible liabilities at preliminary fair value			(4,487,000)
Deferred tax liabilities			85,000
Goodwill			4,902,000
CGC Technology | Technology
Business Acquisition [Line Items]
Identifiable intangible assets	5,000,000	$ 5,000,000	5,000,000	5,000,000
Measurement Period Adjustments
Estimated useful lives		20 years
CGC Technology | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	6,500,000	$ 7,000,000	6,500,000	6,500,000
Measurement Period Adjustments
Identifiable intangible assets			(500,000)
Estimated useful lives		15 years
CGC Technology | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets	$ 800,000	$ 800,000	$ 800,000	$ 800,000
Measurement Period Adjustments
Estimated useful lives		5 years