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Employee Benefit Plans - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 27, 2014
Dec. 28, 2013
Dec. 29, 2012
Defined Benefit Plan Disclosure [Line Items]      
Matching contribution, percent 3.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent 1.50%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent 1.50%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Employer contributions to plan $ 800,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 400,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 400,000us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Employer contributions to Swiss Plan during fiscal 2015 700,000us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear    
Employee contributions to Swiss Plan during fiscal 2015 700,000cohu_DefinedBenefitPlanEstimatedFutureEmployeeContributionsInNextFiscalYear    
Estimated benefit payments, 2015 700,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths    
Estimated benefit payments, 2016 700,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo    
Estimated benefit payments, 2017 700,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree    
Estimated benefit payments, 2018 700,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour    
Estimated benefit payments, 2019 800,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive    
Estimated benefit payments, thereafter through 2024 5,500,000us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter    
Plan assets 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets    
Weighted average discount rate of accumulated post-retirement benefit obligation 3.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate 4.60%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate 3.70%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Assumed annual rates of increase of cost of health benefits 8.00%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear    
Assumed annual rates of decrease for cost of health benefits 0.50%cohu_DefinedBenefitPlanDecreaseInAssumedHealthcareCostTrendRatePercentage    
Defined benefit plan cost of health benefit, trend rate 5.00%us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate    
Defined benefit plan cost of health benefit, year that rate reaches ultimate rate 2021    
Result of one percent increase in net periodic benefit cost 14,000us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents    
Result of one percent decrease in net periodic benefit cost (11,000)us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1    
Result of one percent increase in accumulated post-retirement benefit obligation 363,000us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation    
Result of one percent decrease in accumulated post-retirement benefit obligation (297,000)us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1    
Percentage increase (decrease) in health care cost trend rates 1.00%cohu_PercentageOfIncreaseDecreaseInHealthCareCostTrendRate    
Payroll liability in accrued compensation and benefits 2,600,000us-gaap_DeferredCompensationLiabilityCurrent 2,300,000us-gaap_DeferredCompensationLiabilityCurrent  
Cash surrender value of the related life insurance policies 2,400,000us-gaap_CashSurrenderValueOfLifeInsurance 2,100,000us-gaap_CashSurrenderValueOfLifeInsurance  
Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target allocations for plan assets, Percentage 76    
Real Estate Investments [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target allocations for plan assets, Percentage 11    
Alternative Investments [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target allocations for plan assets, Percentage 9    
Cash [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target allocations for plan assets, Percentage 3    
Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target allocations for plan assets, Percentage 1    
Swiss Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Amounts recognized in accumulated other comprehensive income related to the Swiss Plan unrecognized net actuarial gain (loss) (2,400,000)us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
1,000,000us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Net periodic benefit cost 897,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
972,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Weighted average discount rate of accumulated post-retirement benefit obligation 1.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
2.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_PlanNameAxis
= cohu_SwissDefinedBenefitPlanMember
 
Post-retirement Health benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Net periodic benefit cost $ 100,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
$ 100,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
$ 300,000us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember