Acquisitions (Fair Value of Assets Acquired and Liabilities Assumed) (Details) - USD ($)			6 Months Ended
	Jul. 31, 2020	Jan. 27, 2020	Jul. 31, 2020	Jul. 31, 2019
Preliminary allocation of aggregate purchase price:
Goodwill	$ 330,519,000		$ 330,519,000	$ 310,489,000
CGC
Business Acquisition [Line Items]
Payable in cash	12,075,000	$ 12,075,000
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
Preliminary allocation of aggregate purchase price:
Cash and cash equivalents	160,000	160,000	160,000
Current assets	4,904,000	4,390,000	4,904,000
Property, plant and equipment	697,000	1,457,000	697,000
Operating lease assets	924,000	924,000	924,000
Deferred tax assets, non-current	470,000	1,075,000	470,000
Non-current assets	89,000	0	89,000
Contract liabilities	(6,890,000)	(6,890,000)	(6,890,000)
Accrued warranty obligations	(1,000,000)	(1,000,000)	(1,000,000)
Other current liabilities	(3,104,000)	(6,198,000)	(3,104,000)
Non-current liabilities	(1,327,000)	(1,329,000)	(1,327,000)
Net tangible liabilities at preliminary fair value	(5,077,000)	(7,411,000)	(5,077,000)
Deferred tax liabilities	(2,967,000)	(2,091,000)	(2,967,000)
Goodwill	15,894,000	20,852,000	15,894,000
Preliminary allocation of aggregate purchase price	23,650,000	23,650,000	23,650,000
Measurement Period Adjustments
Current assets			514,000
Property, plant and equipment			(760,000)
Deferred tax assets, non-current			(605,000)
Non-current assets			89,000
Other current liabilities			3,094,000
Non-current liabilities			2,000
Net tangible liabilities at preliminary fair value			2,334,000
Deferred tax liabilities			(876,000)
Goodwill			(4,958,000)
CGC | Technology
Preliminary allocation of aggregate purchase price:
Identifiable intangible assets	6,700,000	$ 5,000,000	6,700,000
Measurement Period Adjustments
Identifiable intangible assets			1,700,000
Estimated Useful Lives		20 years
CGC | Customer relationships
Preliminary allocation of aggregate purchase price:
Identifiable intangible assets	8,100,000	$ 6,500,000	8,100,000
Measurement Period Adjustments
Identifiable intangible assets			1,600,000
Preliminary allocation of aggregate purchase price			0
Estimated Useful Lives		17 years
CGC | Trade name
Preliminary allocation of aggregate purchase price:
Identifiable intangible assets	$ 1,000,000	$ 800,000	1,000,000
Measurement Period Adjustments
Identifiable intangible assets			$ 200,000
Estimated Useful Lives		5 years