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Employee Benefit Plans - Schedule of Weighted-Average Actuarial Assumptions to Determine Benefit Obligation and Net Periodic Benefit Cost (Detail)
12 Months Ended
Dec. 27, 2014
Dec. 28, 2013
Dec. 29, 2012
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 3.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate 4.60%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate 3.70%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Swiss Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 1.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
2.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Compensation increase 1.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
2.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Discount rate 2.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
1.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Rate of return on Assets 2.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
1.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Compensation increase 2.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
2.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember