v3.8.0.1
Document And Entity Information - shares
9 Months Ended
Sep. 30, 2017
Oct. 19, 2017
Document Information [Line Items]    
Entity Registrant Name COHU INC  
Entity Central Index Key 0000021535  
Trading Symbol cohu  
Current Fiscal Year End Date --12-30  
Entity Filer Category Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Well-known Seasoned Issuer No  
Entity Common Stock, Shares Outstanding (in shares)   28,288,018
Document Type 10-Q  
Document Period End Date Sep. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q3  
Amendment Flag false