Employee Stock Option [Member]
Document And Entity Information
Customer Concentration Risk [Member]
Note To Financial Statement Details Textual
statementsignificantaccountingpoliciespolicies
statementnote1summaryofsignificantaccountingpoliciestables
Rest of the World [Member]
The rest of the world.
statementnote2discontinuedoperationstables
statementnote4goodwillandpurchasedintangibleassetstables
Sales Revenue, Net [Member]
Malaysia [Member]
Information about Malaysia.
statementnote5financialinstrumentsmeasuredatfairvaluetables
Intel [Member]
Information about Intel.
statementnote6employeebenefitplanstables
Restricted Stock Units (RSUs) [Member]
statementnote7incometaxestables
Concentration Risk Benchmark [Axis]
statementnote8segmentandgeographicinformationtables
cohu_IncomeTaxReconciliationSettlementsAdjustmentsAndReleasesFromStatuteExpirations
Settlements, adjustments and releases from statute expirations
Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements adjustments and releases from statute expiration.
Income taxes payable, including excess stock option exercise benefits
cohu_DeferredTaxLiabilitiesAssetBasisDifferences
Acquisition basis differences
Amount of deferred tax liability attributable to taxable temporary differences from acquisition basis differences.
statementnote9commitmentsandcontingenciestables
Concentration Risk Type [Axis]
cohu_DeferredTaxAssetAcquisitionBasisDifferences
Acquisition basis differences
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from acquisition basis differences.
statementnote10guaranteestables
Concentration Risk Benchmark [Domain]
statementnote11accumulatedothercomprehensiveincomelosstables
us-gaap_AllocatedShareBasedCompensationExpense
Share-based compensation of continuing operations
us-gaap_IncreaseDecreaseInDeferredRevenue
Deferred profit
statementnote12quarterlyfinancialdataunauditedtables
us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax
Total share-based compensation, net of tax
Concentration Risk Type [Domain]
statementscheduleiivaluationandqualifyingaccountstables
statementnote1computationofbasicanddilutedincomelosspersharedetails
us-gaap_IncomeLossFromContinuingOperations
Income (loss) from continuing operations
Income (loss) from continuing operations
statementnote1prioryearreclassificationsdetails
statementnote1propertyplantandequipmentdetails
us-gaap_DefinedBenefitPlanActuarialGainLoss
Actuarial gain (loss)
statementnote2summaryofoperatingresultsdetails
us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation
Foreign currency exchange adjustment
statementnote2summaryofbalancesheetinformationofdiscontinuedvideocamerasegmentdetails
Net income (loss)
Net income (loss)
Net loss
statementnote4purchasedintangibleassetssubjecttoamortizationdetails
Short-term investments
cohu_DeferredTaxAssetsInventoryAndWarrantyReserves
Inventory, receivable and warranty reserves
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory and warranty reserves.
statementnote4changesincarryingvalueofgoodwilldetails
statementnote5effectivematuritiesofshortterminvestmentsdetails
cohu_CollectionTermRange
Collection Term Range
The collection term range.
statementnote5shortterminvestmentsbysecuritytypedetails
us-gaap_DefinedBenefitPlanSettlementsBenefitObligation
Settlements
statementnote6netperiodicbenefitcostofswissplandetails
statementnote5assetsmeasuredatfairvalueonrecurringbasisdetails
us-gaap_IncreaseDecreaseInOtherAccruedLiabilities
Other accrued liabilities
statementnote6weightedaverageactuarialassumptionstodeterminebenefitobligationandnetperiodicbenefitcostdetails
us-gaap_IncreaseDecreaseInAccruedLiabilities
Accrued compensation, warranty and other liabilities
statementnote6benefitobligationfairvalueofplanassetsfundedstatusandliabilityofswissplandetails
statementnote6stockoptionactivityundersharebasedcompensationplansdetails
us-gaap_DefinedBenefitPlanPlanAmendments
Plan change
statementnote6postretirementbenefitobligationtofundedstatusandliabilitydetails
statementnote6restrictedstockunitactivityundersharebasedcompensationplansdetails
statementnote6stockoptionsoutstandingandexercisabledetails
statementnote6reportedsharebasedcompensationinconsolidatedfinancialstatementsdetails
statementnote7componentsofprovisionbenefitforincometaxesforcontinuingoperationsdetails
statementnote6performancebasedstockunitactivityundersharebasedcompensationplansdetails
statementnote6weightedaverageassumptionstovaluesharebasedawardsgranteddetails
us-gaap_UndistributedEarningsOfForeignSubsidiaries
Undistributed Earnings of Foreign Subsidiaries
statementnote7reconciliationofincometaxcomputedatusfederalstatutorytaxratetoprovisionbenefitforincometaxesforcontinuingoperationsdetails
statementnote7reconciliationofincometaxcomputedatusfederalstatutorytaxratetoprovisionbenefitforincometaxesforcontinuingoperationsdetailsparentheticals
statementnote7incomelossbeforeincometaxesfromcontinuingoperationsdetails
statementnote7componentsofdeferredtaxassetsandliabilitiesdetails
All Countries [Domain]
statementnote8summaryofnetsalestocustomersattributedtocountriesdetails
statementnote8summaryofpropertyplantandequipmentandotherlonglivedassetsingeographicalareadetails
statementnote7reconciliationofgrossunrecognizedtaxbenefitsdetails
Statement of Comprehensive Income [Abstract]
statementnote8customerscomprising10ofconsolidatedsalesdetails
statementnote11componentsofothercomprehensiveincomelossdetails
us-gaap_AmortizationOfIntangibleAssets
Amortization of Intangible Assets
Allowance for Doubtful Accounts [Member]
statementnote11componentsofaccumulatedothercomprehensiveincomenetoftaxdetails
statementnote9futureminimumleasepaymentsdetails
statementnote10changesinaccruedwarrantydetails
cohu_AmountIncludesFromAcquisitionAndForeignCurrencyImpact
Amount Includes from Acquisition and Foreign Currency Impact
The amount includes from acquisition and foreign currency impact.
Notes To Financial Statements [Abstract]
Notes To Financial Statements
statementscheduleiivaluationandqualifyingaccountsdetails
us-gaap_GoodwillImpairmentLoss
Goodwill, Impairment Loss
statementnote12summaryofquarterlyfinancialdatadetails
Defined Benefit Plan, Asset Categories [Axis]
Plan Asset Categories [Domain]
Changes in current assets and liabilities, excluding effects from acquisitions and divestitures:
us-gaap_AvailableForSaleSecuritiesDebtSecurities
cohu_IncreaseDecreaseOfEarningPerShareDueToImpactOfTaxHolidays
Increase (Decrease) of Earning Per Share Due To Impact Of Tax Holidays
The increase or decrease of earning per share due to impact of tax holidays.
Regulatory Income Taxes, Policy [Policy Text Block]
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by operating activities
Weighted average shares used in computing income (loss) per share:
us-gaap_SaleLeasebackTransactionAnnualRentalPayments
Sale Leaseback Transaction, Annual Rental Payments
Cash and cash equivalents
Cash and cash equivalents at beginning of year
Cash and cash equivalents at end of year
us-gaap_SaleLeasebackTransactionDeferredGainGross
Sale Leaseback Transaction, Deferred Gain, Gross
us-gaap_SaleLeasebackTransactionCurrentPeriodGainRecognized
Gain on sale of facility (Note 3)
Sale Leaseback Transaction, Current Period Gain Recognized
us-gaap_SaleLeasebackTransactionDeferredGainNet
Sale Leaseback Transaction, Deferred Gain, Net
Sale Leaseback Transaction, Name [Domain]
Defined Benefit Retirement Plans [Member]
The defined benefit retirement plans.
Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]
Research and development
Defined Benefit Plan and Other Postretirement Benefit Plan [Domain]
Sale Leaseback Transaction Disclosure [Text Block]
Sale Leaseback Transaction, Description [Axis]
us-gaap_DeferredTaxAssetsOther
Other
us-gaap_DeferredIncomeTaxLiabilities
Total deferred tax liabilities
cohu_CumulativeThreeYearPreTaxIncomeLoss
Cumulative Three Year Pre-tax Income (Loss)
The amount of cumulative three year pre-tax income (loss).
us-gaap_DeferredTaxAssetsGross
Gross deferred tax assets
Schedule of Assumptions Used [Table Text Block]
Performance Stock Units [Member]
The performance stock units.
Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block]
us-gaap_DeferredTaxAssetsNet
Total deferred tax assets
Schedule of Net Benefit Costs [Table Text Block]
Summary of Valuation Allowance [Table Text Block]
us-gaap_DeferredTaxAssetsValuationAllowance
Deferred Tax Assets, Valuation Allowance
Less valuation allowance
us-gaap_SaleLeasebackTransactionGrossProceedsInvestingActivities
Sale Leaseback Transaction, Gross Proceeds, Investing Activities
Schedule of Net Funded Status [Table Text Block]
Fair Value Measurement, Policy [Policy Text Block]
Schedule of Nonvested Performance-based Units Activity [Table Text Block]
Selling, general and administrative
Net cash received from sale of facility
Sale Leaseback Transaction, Net Proceeds, Investing Activities
Segment Reporting, Policy [Policy Text Block]
us-gaap_TableTextBlock
Notes Tables
cohu_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlansFutureIssuance
Stock Issued During Period Shares Employee Stock Purchase Plans Future Issuance
stock issued during period shares employee stock purchase plans future issuance.
cohu_DisposalGroupIncludingDiscontinuedOperationDeferredProfit
Deferred Profit
Amount classified as deferred profit attributable to disposal group held for sale or disposed of.
cohu_PercentageOfFairValueToDeterminePriceOfCommonStock
Percentage of Fair Value to Determine Price of Common Stock
Percentage of the Fair Value to Determine the price of common stock.
Comprehensive Income, Policy [Policy Text Block]
Earnings Per Share, Policy [Policy Text Block]
us-gaap_DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
Accounts receivable, net
us-gaap_DisposalGroupIncludingDiscontinuedOperationInventory1
Inventories
Foreign Currency Transactions and Translations Policy [Policy Text Block]
Unvested Stock Options [Member]
The unvested stock options.
Unvested Restricted Stock Units [Member]
The unvested restricted stock units.
cohu_DefinedBenefitPlanDecreaseInAssumedHealthcareCostTrendRatePercentage
Defined Benefit Plan Decrease In Assumed Healthcare Cost Trend Rate Percentage
The defined benefit plan decrease in assumed healthcare cost trend rate percentage.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]
us-gaap_DeferredTaxAssetsDeferredIncome
Deferred profit and gain on facility sale
Common stock, shares outstanding (in shares)
cohu_UnrecognizedTaxBenefitsInterestExpenseNetOfAccruedInterestReversed
Unrecognized Tax Benefits, Interest Expense, Net of Accrued Interest Reversed
Amount of interest expense net of accrued interest reversed for an underpayment of income taxes.
Discontinued Operations, Policy [Policy Text Block]
us-gaap_OtherAccruedLiabilitiesCurrent
Other accrued liabilities
us-gaap_DeferredTaxAssetsTaxCreditCarryforwards
Tax credit carryforwards
Accrued warranty
Money Market Funds [Member]
us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansTaxPortionAttributableToParent
Adjustments related to postretirement benefits
us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
Net operating loss carryforwards
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]
us-gaap_OtherComprehensiveIncomeForeignCurrencyTranslationAdjustmentTaxPortionAttributableToParent
Foreign currency translation adjustments
Cash [Member]
us-gaap_ComprehensiveIncomeNetOfTax
Comprehensive loss
us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Purchases of property, plant and equipment
us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits
Accrued employee benefits
Advertising Costs, Policy [Policy Text Block]
us-gaap_Assets
Total assets
us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost
Stock-based compensation
Current liabilities:
Fair Value, Measurement Inputs, Disclosure [Text Block]
Revenue Recognition Leases [Policy Text Block]
Property plant and equipment, net
Property plant and equipment, net
Net property, plant and equipment
us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract
Lessee Leasing Arrangements, Operating Leases, Term of Contract
Goodwill
Balance
Balance
us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm
Lessee Leasing Arrangements, Operating Leases, Renewal Term
us-gaap_NumberOfOperatingSegments
Number of Operating Segments
Property, plant and equipment
us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Less accumulated depreciation and amortization
Swiss Plan [Member]
Information about the Swiss Plan.
Net sales
Net sales
us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Change in unrealized gain/loss on investments
Additions (Reductions) Charged (Credited) to Expense
Valuation Allowances and Reserves, Charged to Cost and Expense
Deductions/ Write-offs
Additions (Reductions) Not Charged to Expense
us-gaap_ValuationAllowancesAndReservesBalance
Balance
Balance
Segment Reporting Disclosure [Text Block]
us-gaap_DeferredTaxLiabilities
Net deferred income tax assets (liabilities)
us-gaap_DeferredTaxLiabilitiesOther
Other
Reserve for Excess and Obsolete Inventories [Member]
Information about the reserve for excess and obsolete inventories.
Machinery, Equipment and Software [Member]
Tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment and collection of computer programs and related data that provide instructions to a computer.
cohu_PercentageOfRevenueRecognizedUponShipmentAndPassageOfTitle
Percentage of Revenue Recognized upon Shipment and Passage of Title
The percentage of revenue recognized upon shipment and passage of title.
cohu_IncreaseDecreaseInAccumulatedOtherComprehensiveIncome
Increase (Decrease) in Accumulated Other Comprehensive Income
The increase decrease in accumulated other comprehensive income.
Post-retirement Health benefits [Member]
The post-retirement health benefits.
Inventory Valuation Reserve [Member]
Intangible assets, net
us-gaap_DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible
Decrease in Unrecognized Tax Benefits is Reasonably Possible
us-gaap_FiniteLivedIntangibleAssetsGross
Gross Carrying Amount
Sales and maturities of short-term investments
us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Accumulated Amortization
us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Net periodic costs
Defined Benefit Plan, Net Periodic Benefit Cost
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]
us-gaap_DisclosureTextBlockAbstract
Notes to Financial Statements
us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment
Depreciation and fixed asset related
Real Estate Investments [Member]
This element represents direct equity investments in real estate projects
Valuation Allowances and Reserves [Domain]
Valuation Allowances and Reserves Type [Axis]
Alternative Investments [Member]
Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds.
UNITED STATES
us-gaap_DeferredIncomeTaxExpenseBenefit
Total deferred
Deferred income taxes
us-gaap_IncomeTaxCreditsAndAdjustments
Income Tax Credits and Adjustments
us-gaap_CurrentStateAndLocalTaxExpenseBenefit
U.S. State
us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit
U.S. State
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
Granted (in shares)
Property, Plant and Equipment [Table Text Block]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
Cancelled (in shares)
Cash paid (refunded) during the year for income taxes
Supplemental disclosure of cash flow information:
us-gaap_CurrentIncomeTaxExpenseBenefit
Total current
us-gaap_LiabilitiesAndStockholdersEquity
us-gaap_DeferredForeignIncomeTaxExpenseBenefit
Foreign
Change in projected benefit obligation:
us-gaap_CurrentForeignTaxExpenseBenefit
Foreign
us-gaap_ForeignCurrencyTransactionGainLossRealized
Foreign Currency Transaction Gain (Loss), Realized
us-gaap_DeferredFederalIncomeTaxExpenseBenefit
U.S. Federal
us-gaap_CurrentFederalTaxExpenseBenefit
U.S. Federal
Accumulated other comprehensive loss
Total accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss), Net of Tax
Retained earnings
cohu_DefinedBenefitPlanNetPeriodicBenefitIncome
Defined Benefit Plan, Net Periodic Benefit Income
The total amount of net periodic benefit income for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.
us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears
2019
us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears
2020
Change in plan assets:
us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter
Thereafter
us-gaap_OperatingLeasesFutureMinimumPaymentsDue
Total
us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan
Shares issued under employee stock purchase plan
us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Stock Issued During Period, Shares, Employee Stock Purchase Plans
us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent
2016
us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears
2017
us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears
2018
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Comprehensive Income (Loss) Note [Text Block]
us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Exercised (in shares)
us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
Exercise of stock options
us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross
Shares issued for restricted stock units vested
PHILIPPINES
us-gaap_PaymentsToAcquireShortTermInvestments
Purchases of short-term investments
us-gaap_DeferredTaxAssetsLiabilitiesNetNoncurrent
Noncurrent deferred income tax assets
us-gaap_StockRepurchasedAndRetiredDuringPeriodValue
Repurchase and retirement of stock
Capitalized facility under build-to-suit lease
us-gaap_IncreaseDecreaseInOtherNoncurrentAssets
Other assets
us-gaap_IncreaseDecreaseInInventories
Inventories
us-gaap_DividendsCommonStockCash
Cash dividends - $0.24 per share
us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
Share-based compensation expense
SINGAPORE
Interest income
Common stock, $1 par value; 60,000 shares authorized, 26,240 shares issued and outstanding in 2015 and 25,692 shares in 2014
us-gaap_IntangibleAssetsNetIncludingGoodwill
Goodwill and other intangible assets, net
Common stock, shares issued (in shares)
Common stock, shares authorized (in shares)
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive
Finite-Lived Intangible Assets, Amortization Expense, after Year Five
us-gaap_IncreaseDecreaseInAccountsReceivable
Accounts receivable
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive
Finite-Lived Intangible Assets, Amortization Expense, Year Five
Common stock, par value (in dollars per share)
us-gaap_GoodwillTranslationAdjustments
Impact of currency exchange
cohu_DeferredProfit
Deferred profit
Deferred Profit
The carrying value of deferred revenue, net of expenses, as of the balance sheet date that is expected to be recognized as such within one year or the normal operating cycle, if longer.
Preferred stock, $1 par value; 1,000 shares authorized, none issued
Work in process
Finished goods
New Accounting Pronouncements, Policy [Policy Text Block]
Raw materials and purchased parts
us-gaap_IncreaseDecreaseInOtherOperatingAssets
Other current assets
Cost of sales
us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
Accumulated net currency translation adjustments
Schedule of Product Warranty Liability [Table Text Block]
GERMANY
us-gaap_GrossProfit
Gross profit
Trade Names [Member]
CHINA
cohu_PercentageOfRevenueRecognizedUponCustomerAcceptance
Percentage of Revenue Recognized upon Customer Acceptance
The percentage of revenue recognized upon customer acceptance.
SWITZERLAND
us-gaap_ProductWarrantyAccrualWarrantiesIssued
Warranty accruals
us-gaap_ProductWarrantyAccrualAdditionsFromBusinessAcquisition
Warranty liability assumed
us-gaap_ProductWarrantyAccrualPayments
Warranty payments
us-gaap_FiniteLivedIntangibleAssetUsefulLife
Finite-Lived Intangible Asset, Useful Life
Schedule of Finite-Lived Intangible Assets [Table Text Block]
Asset Class [Axis]
us-gaap_ConcentrationRiskPercentage1
Net sales percentage
Asset Class [Domain]
us-gaap_CashSurrenderValueOfLifeInsurance
Cash Surrender Value of Life Insurance
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months
us-gaap_OperatingIncomeLoss
Income (loss) from operations
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo
Finite-Lived Intangible Assets, Amortization Expense, Year Two
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree
Finite-Lived Intangible Assets, Amortization Expense, Year Three
us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour
Finite-Lived Intangible Assets, Amortization Expense, Year Four
us-gaap_IncreaseDecreaseInAccountsPayable
Accounts payable
us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
Accumulated net adjustments related to postretirement benefits
Finite-Lived Intangible Assets by Major Class [Axis]
Finite-Lived Intangible Assets, Major Class Name [Domain]
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
Rasco Technology [Member]
Represents information about Rasco technology.
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options
Issuance of stock, net
Cost of Sales [Member]
Amendment Flag
Inventory [Domain]
Inventory [Axis]
Income Tax Disclosure [Text Block]
Vesting [Domain]
Research and Development Expense [Member]
Ismeca Technology [Member]
Represents information about Ismeca technology.
Vesting [Axis]
Income Statement Location [Domain]
Plan Name [Domain]
Income Statement Location [Axis]
Plan Name [Axis]
Lease Arrangement, Type [Domain]
us-gaap_ProductWarrantyAccrual
Beginning balance
Ending balance
Minimum [Member]
Lease Arrangement, Type [Axis]
Maximum [Member]
Range [Axis]
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage
Range [Domain]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Document Fiscal Year Focus
Customer [Axis]
Document Fiscal Period Focus
Semiconductor Equipment [Member]
Semiconductor equipment as a business segment.
Customer [Domain]
Document Period End Date
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized
Current Fiscal Year End Date
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period
us-gaap_CostsAndExpenses
Cost and expenses
Cost and expenses:
Inventory capitalized as capital assets
Represents information about inventory capitalized as property, plant and equipment.
Award Type [Axis]
Entity Current Reporting Status
Entity Voluntary Filers
Operating Leases of Lessee Disclosure [Table Text Block]
Entity Public Float
Entity Filer Category
Machinery and Equipment [Member]
Noncurrent deferred gain on sale of facility (Note 3)
us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent
Other comprehensive income (loss)
Document Type
us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Other comprehensive income (loss)
Other comprehensive income (loss), net of tax
us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1
Other comprehensive income (loss)
Equity Award [Domain]
us-gaap_DeferredRevenue
Deferred Revenue
us-gaap_ProductWarrantyAccrualNoncurrent
Product Warranty Accrual, Noncurrent
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Selling, General and Administrative Expenses [Member]
us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Income tax benefit
Entity Well-known Seasoned Issuer
us-gaap_GuaranteeObligationsMaximumExposure
Guarantor Obligations, Maximum Exposure, Undiscounted
us-gaap_GuaranteeObligationsCurrentCarryingValue
Guarantor Obligations, Current Carrying Value
us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Exercised (in dollars per share)
us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
Granted (in dollars per share)
us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPortionAttributableToParent
Adjustments related to postretirement benefits
us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
Cancelled (in dollars per share)
cohu_StandardProductWarrantyTerm
Standard Product Warranty Term
Describes the term of the product warranty.
Segments [Domain]
us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Allowance for Doubtful Accounts Receivable, Current
Segments [Axis]
Statement [Table]
Options Outstanding, Weighted Average Exercise Price (in dollars per share)
Outstanding, beginning of year (in dollars per share)
Outstanding, end of year (in dollars per share)
us-gaap_LineOfCredit
Long-term Line of Credit
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Weighted-average grant date fair value per share (in dollars per share)
us-gaap_OtherAccruedLiabilitiesNoncurrent
Other accrued liabilities
Options Outstanding, Weighted Average Remaining Life
Current assets:
us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax
Change in unrealized gain/loss on investments
Options Exercisable (in shares)
Options exercisable at year end (in shares)
Effect of exchange rate changes on cash and cash equivalents
us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Net increase (decrease) in cash and cash equivalents
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value
Options Exercisable, Weighted Average Exercise Price (in dollars per share)
Options exercisable at year end (in dollars per share)
Income Statement [Abstract]
Investing cash flows of discontinued operations
us-gaap_CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations
Operating cash flows of discontinued operations
Schedule of Goodwill [Table Text Block]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash used in financing activities
Geographical [Axis]
us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent
Foreign currency translation adjustments
Employee Stock Purchase Plan [Member]
Employee stock purchase plan.
Number Outstanding (in shares)
Outstanding, beginning of year (in shares)
Outstanding, end of year (in shares)
Vest on Second and Third Anniversary Grant Date [Member]
Represents information about vests on second and third anniversary grant date.
Equity Based Performance Stock Units [Member]
Equity based performance stock units.
cohu_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfSharesAvailableForIssue
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Shares Available for Issue
Share based compensation arrangement by share based payment award percentage of shares available for issue.
us-gaap_StockholdersEquity
Balance
Balance
Total stockholders' equity
Goodwill and Intangible Assets Disclosure [Text Block]
us-gaap_PaymentsOfDividendsCommonStock
Cash dividends paid
Financial Statement Line Items with Differences in Reported Amount and Reporting Currency Denominated Amounts [Domain]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Risk-free interest rate
Preferred stock, shares issued (in shares)
Preferred stock, shares authorized (in shares)
Other comprehensive income (loss), net of tax:
us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
Due in one year or less, amortized cost
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Expected volatility
Preferred stock, par value (in dollars per share)
Information by Financial Statement Line Item [Axis]
us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Expected term (years)
us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
Foreign currency translation adjustments
Changes in cumulative translation adjustment
us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
Adjustments related to postretirement benefits
Adjustments related to postretirement benefits, net of tax
us-gaap_InventoryNet
Net inventory
Range of Exercise Prices, Upper (in dollars per share)
Range of Exercise Prices, Lower (in dollars per share)
Other current assets
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain]
us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
Due in one year or less, estimated fair value
us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
Change in unrealized gain/loss on investments
Changes in unrealized gains and losses on investments, net of tax
Exercise Price Range [Axis]
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Dividend yield
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Cancelled, Units (in shares)
New Accounting Pronouncement, Early Adoption [Table Text Block]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Outstanding, beginning of year, Units (in shares)
Outstanding, end of year, Units (in shares)
New Accounting Pronouncement, Early Adoption [Axis]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Granted, Units (in shares)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Released, Units (in shares)
New Accounting Principles, Early Adoption [Domain]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value
us-gaap_CommonStockDividendsPerShareDeclared
Cash dividend, per share (in dollars per share)
Accounts receivable, net
Inventories:
Paid-in capital
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Released, Wt. Avg. Fair Value (in dollars per share)
Stockholders' equity:
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Granted, Wt. Avg. Fair Value (in dollars per share)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Outstanding, beginning of year, Wt. Avg. Fair Value (in dollars per share)
Outstanding, end of year, Wt. Avg. Fair Value (in dollars per share)
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Cancelled, Wt. Avg. Fair Value (in dollars per share)
Commitments Contingencies and Guarantees [Text Block]
Foreign Government Debt Securities [Member]
Entity Registrant Name
Entity Central Index Key
Available-for-sale Securities [Table Text Block]
Other assets
Contingencies Disclosure [Text Block]
Debt Securities [Member]
Entity Common Stock, Shares Outstanding (in shares)
Commitments and contingencies
us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
Total liabilities
us-gaap_DeferredTaxAssetsLiabilitiesNetCurrent
Current deferred income tax assets
Trading Symbol
Scenario [Axis]
Scenario, Unspecified [Domain]
us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued
us-gaap_AssetsCurrent
Total current assets
Restatement Adjustment [Member]
Scenario, Previously Reported [Member]
Current assets of discontinued operations (Note 2)
Total current assets
us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
Other current assets
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign
Foreign
Investments, Gross Unrealized Gains
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic
U.S.
Investments, Gross Unrealized Losses
Loss on disposal and impairment of fixed assets
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block]
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country [Table Text Block]
us-gaap_LiabilitiesCurrent
Total current liabilities
Basic:
us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
Loss from discontinued operations (in dollars per share)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation
us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation
Inventory, Policy [Policy Text Block]
us-gaap_DepreciationDepletionAndAmortization
Depreciation and amortization
us-gaap_DefinedBenefitPlanYearThatRateReachesUltimateTrendRate
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate
us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components
us-gaap_ProceedsFromDivestitureOfBusinesses
Proceeds from Divestiture of Businesses
us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components
Fair Value, Inputs, Level 1 [Member]
us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year
Fair Value Hierarchy [Domain]
Fair Value, Inputs, Level 3 [Member]
us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate
Fair Value, Inputs, Level 2 [Member]
us-gaap_Depreciation
Depreciation
Property, Plant and Equipment, Policy [Policy Text Block]
us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss
Operating loss before income taxes
Fair Value, Hierarchy [Axis]
Property, Plant and Equipment, Type [Axis]
us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Payment for purchase of Ismeca, net of cash received
us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year
Property, Plant and Equipment, Type [Domain]
Building Improvements [Member]
Condensed Statement of Comprehensive Income [Table Text Block]
Building and Building Improvements [Member]
us-gaap_DeferredTaxLiabilitiesCurrent
Current deferred income tax liabilities (included in other accrued liabilities)
us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Defined Contribution Plan, Employer Discretionary Contribution Amount
Income Tax Authority [Axis]
Land, Buildings and Improvements [Member]
Income Tax Authority [Domain]
Land and Land Improvements [Member]
Disposal Group Name [Domain]
us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay
State and Local Jurisdiction [Member]
Disposal Group Name [Axis]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]
Domestic Tax Authority [Member]
Foreign Tax Authority [Member]
Disposal Groups, Including Discontinued Operations [Table Text Block]
Statement of Financial Position [Abstract]
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]
us-gaap_ShareBasedCompensation
Share-based compensation expense
Quarterly Financial Information [Text Block]
Schedule of Quarterly Financial Information [Table Text Block]
Current liabilities of discontinued operations (Note 2)
Total current liabilities
Accrued retiree benefits
us-gaap_PropertyPlantAndEquipmentUsefulLife
Property, Plant and Equipment, Useful Life
Statement of Cash Flows [Abstract]
cohu_DisposalGroupIncludingDiscontinuedOperationContingentConsideration
Disposal Group, Including Discontinued Operation, Contingent Consideration
Amount of contingent consideration receivable for the disposal of assets and liabilities, including discontinued operation.
Statement of Stockholders' Equity [Abstract]
Cohu Electronics [Member]
Represents information about Cohu Electronics, the Company's video camera segment.
cohu_IncreaseDecreaseOfNetIncomeDueToImpactOfTaxHolidays
Increase (Decrease) of Net Income Due to Impact of Tax Holidays
Increase (decrease) in net income due to the impact of tax holidays.
Investments, Amortized Cost
NXP Semiconductors N.V. [Member]
Information pertaining to NXP Semiconductors N.V.
Broadcast Microwave Services, Inc. (“BMS”) [Member]
Represents information about Broadcast Microwave Services,Inc., the Company's microwave communications equipment segment.
cohu_EmployeeServiceSharebasedCompensationDiscontinuedOperations
Discontinued operations
The amount of expense related to discontinued operations for equity-based payment arrangements recognized during the period.
Cash flows from operating activities:
us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions
Gross additions for tax positions of prior years
us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromForeignCurrencyTranslation
Foreign exchange rate impact
us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations
Reductions due to lapse of the statute of limitations
Equity Incentive Plan 2005 [Member]
Information pertaining to the 2005 Equity Incentive Plan.
Loss from discontinued operations, net of tax (Note 2)
Loss, net of tax
Effect of dilutive stock options and restricted stock units (in shares)
us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions
Gross additions for tax positions of current year
Municipal Securities [Member]
Long-term debt securities issued by state, city or local governments or the agencies operated by state, city or local governments.
cohu_AvailableforsaleSecuritiesDebtMaturitiesYearTwoThroughThreeFairValue
Due after one year through three years, estimated fair value
Fair value of available-for-sale debt securities maturing in the second fiscal year through the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
Gain (loss) on disposal of segment
cohu_AvailableforsaleSecuritiesDebtMaturitiesYearTwoThroughThreeAmortizedCostBasis
Due after one year through three years, amortized cost
Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the third fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
Goodwill and Intangible Assets, Policy [Policy Text Block]
us-gaap_DeferredCompensationLiabilityCurrent
Deferred Compensation Liability, Current
us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Unrecognized Tax Benefits that Would Impact Effective Tax Rate
us-gaap_UnrecognizedTaxBenefits
Balance at beginning of year
Balance at end of year
us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriod
Income tax provision
us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax
Gain (loss) from disposal of segment
us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationDuringPhaseOutPeriodNetOfTax
Net sales
us-gaap_EarningsPerShareDiluted
Net income (loss) (in dollars per share)
Commitments and Contingencies, Policy [Policy Text Block]
us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount
us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
(in shares)
Diluted (in shares)
Accrued compensation and benefits
us-gaap_TaxCreditCarryforwardAmount
Tax Credit Carryforward, Amount
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Total
Accounts payable
Income tax provision (benefit)
Cash flows from financing activities:
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash provided by (used in) investing activities
us-gaap_PaymentsForProceedsFromOtherInvestingActivities
Other assets
Income taxes payable
Diluted:
Weighted average common shares outstanding (in shares)
Basic (in shares)
us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
Income (loss) from continuing operations (in dollars per share)
us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap_DisposalGroupIncludingDiscontinuedOperationAccruedLiabilities
Other accrued current liabilities
Standard Product Warranty, Policy [Policy Text Block]
us-gaap_EarningsPerShareBasic
Net income (loss) (in dollars per share)
us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
Loss from discontinued operations (in dollars per share)
Income Statement Information [Member]
Information by each relevant line item on the Income Statement.
Balance Sheet Information [Member]
Information by each relevant line item on the balance sheet.
cohu_InitialCashProceedsFromDivestitureOfBusinesses
Initial Cash Proceeds from Divestiture of Businesses
The initial cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period, not including contingent consideration or working capital adjustment.
us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
Income (loss) from continuing operations (in dollars per share)
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Investment Type [Axis]
Class of Stock [Axis]
us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Fair value of plan assets at beginning of year
Fair value of plan assets at end of year
Plan assets at end of year
Significant Accounting Policies [Text Block]
Accounting Policies [Abstract]
Cash and Cash Equivalents, Policy [Policy Text Block]
Basis of Accounting, Policy [Policy Text Block]
us-gaap_DefinedBenefitPlanFundedStatusOfPlan
Funded status
Net liability at end of year
us-gaap_GainLossOnSaleOfProperties
Gain on sale of facility
us-gaap_DefinedBenefitPlanBenefitsPaid
Benefits paid
Benefits paid
Range 1 [Member]
Information by range of option prices pertaining to options granted.
us-gaap_DefinedBenefitPlanSettlementsPlanAssets
Settlements
Municipal Bonds [Member]
us-gaap_DefinedBenefitPlanBenefitObligation
Benefit obligation at beginning of year
Benefit obligation at end of year
cohu_LesseeLeasingArrangementsOperatingLeasesNumberOfRenewalOptions
Lessee Leasing Arrangements, Operating Leases, Number of Renewal Options
Represents the lessee operating lease arrangement number of renewal options.
us-gaap_OperatingLossCarryforwards
Operating Loss Carryforwards
us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesPlanAssets
Foreign currency exchange adjustment
cohu_ContingentConsiderationReceivableFairValue
Contingent Consideration Receivable, Fair Value
Represents contingent consideration receivable fair value.
us-gaap_DefinedBenefitPlanContributionsByPlanParticipants
Participant contributions
Participant contributions
us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets
Return on assets, net of actuarial loss
Investments [Domain]
Range 2 [Member]
Information by range of option prices pertaining to options granted.
Range 3 [Member]
Information by range of option prices pertaining to options granted.
us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation
Accumulated benefit obligation at beginning of year
Accumulated benefit obligation at end of year
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
Expected return on assets
us-gaap_DefinedBenefitPlanInterestCost
Interest cost
Interest cost
New Accounting Pronouncement, Early Adoption, Effect [Member]
us-gaap_DefinedBenefitPlanServiceCost
Service cost
Service cost
us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax
Defined Benefit Plan, Accumulated Other Comprehensive Income Net Gains (Losses), after Tax
AOCI Attributable to Parent [Member]
Equity Securities [Member]
Sale-leaseback of Poway Facility [Member]
Information pertaining to the sale-leaseback of Poway Facility.
Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]
Statement [Line Items]
Lease 1 [Member]
Information pertaining to the first lease.
Lease 2 [Member]
Information pertaining to the second lease.
cohu_PercentageOfFacilityToBeConsolidated
Percentage of Facility to be Consolidated
Represents the percentage area of the facility to be occupied.
cohu_SaleLeasebackTransactionDeferredGainAmortizationPeriod
Sale Leaseback Transaction, Deferred Gain, Amortization Period
The amortization period of the deferred gain in a sale leaseback transaction.
cohu_LesseeLeasingArrangementsOperatingLeasesAdjustmentsAndProRataShareOfPropertyOperatingCosts
Lessee Leasing Arrangements, Operating Leases, Adjustments and Pro Rata Share of Property Operating Costs
Term of the lessee's leasing arrangement providing a percentage of annual adjustments for inflation and a pro rata share of property operating costs.
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]
Investments Classified by Contractual Maturity Date [Table Text Block]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]
us-gaap_LeaseAndRentalExpense
Operating Leases, Rent Expense
Deferred income taxes
Noncurrent deferred income tax liabilities
Accrued retirement benefits
Certificates of Deposit [Member]
us-gaap_IncomeTaxReconciliationOtherReconcilingItems
Other, net
us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
U.S. Federal statutory tax rate
us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate
Fair Value, Assets Measured on Recurring Basis [Table Text Block]
us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance
Change in valuation allowance
Noncurrent liabilities of discontinued operations (Note 2)
Noncurrent liabilities
us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
Compensation increase
us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Discount rate
us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Rate of return on Assets
us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease
Compensation increase
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
Defined Benefit Plan, Expected Future Benefit Payments, Year Five
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
Defined Benefit Plan, Expected Future Benefit Payments, Year Four
us-gaap_DividendsPayableCurrentAndNoncurrent
Dividends declared but not yet paid
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
Defined Benefit Plan, Expected Future Benefit Payments, Year Three
us-gaap_DefinedBenefitPlanContributionsByEmployer
Employer contributions
us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Line of Credit Facility, Maximum Borrowing Capacity
Equity Component [Domain]
Equity Components [Axis]
us-gaap_IncomeTaxReconciliationTaxCreditsResearch
Federal tax credits
us-gaap_IncomeTaxReconciliationForeignIncomeTaxRateDifferential
Foreign income taxed at different rates
Concentration Risk, Credit Risk, Policy [Policy Text Block]
us-gaap_IncomeTaxReconciliationStateAndLocalIncomeTaxes
State income taxes, net of federal tax benefit
us-gaap_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate
Tax provision (credit) at U.S. 35% statutory rate
Common Stock [Member]
Noncurrent income tax liabilities
Additional Paid-in Capital [Member]
us-gaap_PolicyTextBlockAbstract
Accounting Policies
us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
Settlements
Retained Earnings [Member]
us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
Defined Benefit Plan, Target Plan Asset Allocations
us-gaap_IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost
Stock-based compensation on which no tax benefit provided
us-gaap_AssetsFairValueDisclosureRecurring
Assets fair value, recurring
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
Defined Benefit Plan, Expected Future Benefit Payments, Year Two