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Employee Benefit Plans - Schedule of Stock Options Outstanding and Exercisable (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 12 Months Ended
Dec. 27, 2014
Dec. 28, 2013
Dec. 29, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options Outstanding, Number Outstanding 2,435us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,086us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,113us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,112us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Options Outstanding Approximate Wt. Avg. Remaining Life (Years) 5 years      
Options Outstanding, Wt. Avg. Ex. Price $ 11.67us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 11.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 12.62us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 13.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Options Exercisable, Number Exercisable 1,901us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber 2,195us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber 2,209us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber  
Options Exercisable, Wt. Avg. Ex. Price $ 12.08us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice $ 12.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice $ 13.52us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice  
Range of Exercise Prices $ 7.32 - $10.98 [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of Exercise Prices, minimum $ 7.32us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Range of Exercise Prices, maximum $ 10.98us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Options Outstanding, Number Outstanding 1,402us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Options Outstanding Approximate Wt. Avg. Remaining Life (Years) 6 years 2 months 12 days      
Options Outstanding, Wt. Avg. Ex. Price $ 8.86us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Options Exercisable, Number Exercisable 898us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Options Exercisable, Wt. Avg. Ex. Price $ 8.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePriceOneMember		      
Range of Exercise Prices $10.99 - $16.49 [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of Exercise Prices, minimum $ 10.99us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Range of Exercise Prices, maximum $ 16.49us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Options Outstanding, Number Outstanding 814us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Options Outstanding Approximate Wt. Avg. Remaining Life (Years) 4 years 2 months 12 days      
Options Outstanding, Wt. Avg. Ex. Price $ 14.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Options Exercisable, Number Exercisable 784us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Options Exercisable, Wt. Avg. Ex. Price $ 14.98us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesTwoMember		      
Range of Exercise Prices $16.5 - $24.74 [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of Exercise Prices, minimum $ 16.50us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Range of Exercise Prices, maximum $ 24.74us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Options Outstanding, Number Outstanding 214us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Options Outstanding Approximate Wt. Avg. Remaining Life (Years) 8 months 12 days      
Options Outstanding, Wt. Avg. Ex. Price $ 17.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Options Exercisable, Number Exercisable 214us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Options Exercisable, Wt. Avg. Ex. Price $ 17.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesThreeMember		      
Range of Exercise Prices $24.75 - $37.13 [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of Exercise Prices, minimum $ 24.75us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember		      
Range of Exercise Prices, maximum $ 37.13us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember		      
Options Outstanding, Number Outstanding 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember		      
Options Outstanding Approximate Wt. Avg. Remaining Life (Years) 7 months 6 days      
Options Outstanding, Wt. Avg. Ex. Price $ 25.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember		      
Options Exercisable, Number Exercisable 5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember		      
Options Exercisable, Wt. Avg. Ex. Price $ 25.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis
= cohu_RangeOfExercisePricesFourMember