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Segment and Related Information - Additional Information (Detail) (Semiconductor Equipment [Member], Consolidated Net Sales [Member], Customer Concentration Risk [Member])
12 Months Ended
Dec. 27, 2014
Semiconductor Equipment [Member] | Consolidated Net Sales [Member] | Customer Concentration Risk [Member]
 
Segment Reporting Information [Line Items]  
Net sales percentage 10.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_ProductOrServiceAxis
= cohu_SemiconductorEquipmentMember