Acquisitions (Fair Value of Assets Acquired and Liabilities Assumed) (Details) - USD ($)				3 Months Ended			8 Months Ended
	Oct. 31, 2019	Apr. 29, 2019	Feb. 28, 2019	Oct. 31, 2019	Jul. 31, 2019	Oct. 31, 2018	Oct. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 309,871,000			$ 309,871,000	$ 310,489,000		$ 309,871,000
Customer relationships
Measurement Period Adjustments
Estimated Useful Lives				20 years 6 months		20 years 6 months
Solacom
Business Acquisition [Line Items]
Settled in cash	27,328,000		$ 27,328,000
Settled in common stock issued by Comtech	5,606,000		5,606,000
Aggregate purchase price at fair value	32,934,000		32,934,000
Cash and cash equivalents	1,445,000		1,445,000	$ 1,445,000			1,445,000
Current assets	9,897,000		9,896,000	9,897,000			9,897,000
Property, plant and equipment	777,000		777,000	777,000			777,000
Deferred tax assets, non-current	5,478,000		5,059,000	5,478,000			5,478,000
Accrued warranty obligations	(1,431,000)		(1,431,000)	(1,431,000)			(1,431,000)
Current liabilities	(4,477,000)		(4,477,000)	(4,477,000)			(4,477,000)
Contract liabilities, non-current	(1,604,000)		(1,604,000)	(1,604,000)			(1,604,000)
Net tangible assets at preliminary fair value	10,085,000		9,665,000	10,085,000			10,085,000
Deferred tax liabilities	(4,153,000)		(4,153,000)	(4,153,000)			(4,153,000)
Goodwill	11,388,000		11,808,000	11,388,000			11,388,000
Allocation of aggregate purchase price	32,934,000		32,934,000	32,934,000			32,934,000
Measurement Period Adjustments
Current assets							1,000
Deferred tax assets, non-current							419,000
Net tangible assets at preliminary fair value							420,000
Goodwill				(420,000)			(420,000)
Solacom | Technology
Business Acquisition [Line Items]
Identifiable intangible assets	6,779,000		$ 6,779,000	6,779,000			6,779,000
Measurement Period Adjustments
Estimated Useful Lives			10 years
Solacom | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	7,007,000		$ 7,007,000	7,007,000			7,007,000
Measurement Period Adjustments
Estimated Useful Lives			20 years
Solacom | Trade name
Business Acquisition [Line Items]
Identifiable intangible assets	1,828,000		$ 1,828,000	1,828,000			1,828,000
Measurement Period Adjustments
Estimated Useful Lives			20 years
GD NG-911 business
Business Acquisition [Line Items]
Aggregate purchase price at fair value	10,000,000	$ 10,000,000
Current assets	4,640,000	4,460,000		4,640,000			4,640,000
Property, plant and equipment	646,000	646,000		646,000			646,000
Deferred tax assets, non-current	3,376,000	3,426,000		3,376,000			3,376,000
Accrued warranty obligations	(5,000,000)	(5,000,000)		(5,000,000)			(5,000,000)
Current liabilities	(3,094,000)	(3,162,000)		(3,094,000)			(3,094,000)
Net tangible assets at preliminary fair value	568,000	370,000		568,000			568,000
Other liabilities	(21,700,000)	(21,700,000)		(21,700,000)			(21,700,000)
Deferred tax liabilities	(518,000)	(518,000)		(518,000)			(518,000)
Goodwill	7,850,000	8,048,000		7,850,000			7,850,000
Allocation of aggregate purchase price	10,000,000	10,000,000		10,000,000			10,000,000
Measurement Period Adjustments
Current assets					180,000
Deferred tax assets, non-current					(50,000)
Current liabilities					68,000
Net tangible assets at preliminary fair value					198,000
Goodwill				(198,000)	$ (198,000)
GD NG-911 business | Technology
Business Acquisition [Line Items]
Identifiable intangible assets	3,500,000	$ 3,500,000		3,500,000			3,500,000
Measurement Period Adjustments
Estimated Useful Lives		15 years
GD NG-911 business | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	$ 20,300,000	$ 20,300,000		$ 20,300,000			$ 20,300,000
Measurement Period Adjustments
Estimated Useful Lives		10 years