Acquisition-Related Restructuring Plan - Details of Future Cash Payments (Details) - USD ($)	Apr. 30, 2017	Jul. 31, 2016	Aug. 01, 2008	Jul. 31, 2008
Restructuring and Related Activities [Abstract]
Future lease payments to be made	$ 2,300,000	$ 3,327,000	$ 2,100,000	$ 2,100,000
Interest expense to be accreted in future periods	250,000
Total remaining payments	$ 2,550,000

Amount accrued to cover estimated present value of facility exit costs related to noncancellable lease obligations assumed in a business combination, net of the present value of estimated sublease income.

No definition available.

Name:	cmtl_BusinessAcquisitionRestructuringCostsFacilityRelatedExitCosts
Namespace Prefix:	cmtl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant