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Schedule II Valuation and Qualifying Accounts (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 28, 2013
Allowance for Doubtful Accounts [Member]  
Valuation and Qualifying Accounts Disclosure [Line Items]  
Amount included from Ismeca Acquisition and foreign currency impact $ 0.4cohu_AmountIncludesFromAcquisitionAndForeignCurrencyImpact
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_AllowanceForDoubtfulAccountsMember
Reserve for Excess and Obsolete Inventories [Member]  
Valuation and Qualifying Accounts Disclosure [Line Items]  
Amount included from Ismeca Acquisition and foreign currency impact $ 6.8cohu_AmountIncludesFromAcquisitionAndForeignCurrencyImpact
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_InventoryValuationReserveMember