XML 15 R1.htm IDEA: XBRL DOCUMENT v3.3.1.900
Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2015
Jan. 31, 2016
Jul. 05, 2015
Entity Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Trading Symbol CGNX    
Entity Registrant Name COGNEX CORP    
Entity Central Index Key 0000851205    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   84,885,334  
Entity Public Float     $ 3,975,185,000