Name:	cohu_BusinessCombinationDebtFinancingCommitmentsExpectedAggregatePrincipalAmountFromCashBridgeFacility
Namespace Prefix:	cohu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The expected aggregate principal amount from a term loan facility originating from a debt financing commitment for the acquisition of a business.

No definition available.

Name:	cohu_BusinessCombinationDebtFinancingCommitmentsExpectedAggregatePrincipalAmountFromTermLoanFacility
Namespace Prefix:	cohu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the percentage of ownership by the acquiree's stockholders after closing in a business combination.

No definition available.

Name:	cohu_BusinessCombinationOwnershipPercentageByAcquireesStockholdersAfterClosing
Namespace Prefix:	cohu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of ownership by the acquirer's stockholders after closing in a business combination.

No definition available.

Name:	cohu_BusinessCombinationOwnershipPercentageByAcquirersStockholdersAfterClosing
Namespace Prefix:	cohu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The amount of shares that holders of the acquired companies stock will receive during a business combination.

No definition available.

Name:	cohu_BusinessCombinationRightToReceivePerShareCommonStock
Namespace Prefix:	cohu_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The issuance of common stock related to a business combination requires stockholders approval if the issuance exceed certain threshold. This element represents the threshold percentage of outstanding common stock before such issuance.

No definition available.

Name:	cohu_BusinessCombinationStockIssuanceByStockholdersApprovalThresholdPercentageOfOutstandingCommonStockBeforeIssuance
Namespace Prefix:	cohu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The amount that the acquiree may be required to pay if the business combination agreement is terminated.

No definition available.

Name:	cohu_BusinessCombinationTerminationFeeByAcquiree
Namespace Prefix:	cohu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

No definition available.

Name:	us-gaap_BusinessAcquisitionSharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Face amount or stated value per share of common stock.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Name:	us-gaap_BusinessAcquisitionAxis=cohu_XcerraMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_LineOfCreditFacilityAxis=cohu_DeutscheBankSecuritiesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_NatureOfExpenseAxis=cohu_TerminationFeeIfCohuFailsToConsummateTheMergerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: