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