Acquisitions (Fair Value of Assets Acquired and Liabilities Assumed) (Details) - USD ($)				3 Months Ended	5 Months Ended
	Jul. 31, 2019	Apr. 29, 2019	Feb. 28, 2019	Jul. 31, 2019	Jul. 31, 2019	Jul. 31, 2018
Business Acquisition [Line Items]
Goodwill	$ 310,489,000			$ 310,489,000	$ 310,489,000	$ 290,633,000
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	9,896,000		9,425,000	9,896,000	9,896,000
Property, plant and equipment	777,000		777,000	777,000	777,000
Deferred tax assets, non-current	5,059,000		5,374,000	5,059,000	5,059,000
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	9,665,000		9,509,000	9,665,000	9,665,000
Deferred tax liabilities	(4,153,000)		(4,153,000)	(4,153,000)	(4,153,000)
Goodwill	11,808,000		11,964,000	11,808,000	11,808,000
Allocation of aggregate purchase price	32,934,000		32,934,000	32,934,000	32,934,000
Measurement Period Adjustments
Current assets					471,000
Deferred tax assets, non-current					(315,000)
Net tangible assets at preliminary fair value					156,000
Goodwill					(156,000)
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	4,460,000	5,790,000		4,460,000	4,460,000
Property, plant and equipment	646,000	646,000		646,000	646,000
Deferred tax assets, non-current	3,426,000	3,292,000		3,426,000	3,426,000
Accrued warranty obligations	(5,000,000)	(5,000,000)		(5,000,000)	(5,000,000)
Current liabilities	(3,162,000)	(3,960,000)		(3,162,000)	(3,162,000)
Net tangible assets at preliminary fair value	370,000	768,000		370,000	370,000
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	8,048,000	7,650,000		8,048,000	8,048,000
Allocation of aggregate purchase price	10,000,000	10,000,000		10,000,000	10,000,000
Measurement Period Adjustments
Current assets				(1,330,000)
Deferred tax assets, non-current				134,000
Current liabilities				798,000
Net tangible assets at preliminary fair value				(398,000)
Goodwill				398,000
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