Guarantees (Detail) $ in Thousands		6 Months Ended
Jul. 06, 2015 USD ($)	Jul. 05, 2015 Category
Guarantees [Abstract]
Disposalgrouplettersofcredit	$ 2,125
Number of categories of letters of credit \| Category		3

Letters of credit disposed as part of discontinued operations

No definition available.

Name:	cgnx_Disposalgrouplettersofcredit
Namespace Prefix:	cgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration