v3.10.0.1
Document And Entity Information - shares
9 Months Ended
Sep. 29, 2018
Oct. 23, 2018
Document Information [Line Items]    
Entity Registrant Name COHU INC  
Entity Central Index Key 0000021535  
Trading Symbol cohu  
Current Fiscal Year End Date --12-29  
Entity Filer Category Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Common Stock, Shares Outstanding (in shares)   40,700,448
Document Type 10-Q  
Document Period End Date Sep. 29, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Amendment Flag false