<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>299</ContextCount>
  <ElementCount>449</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>79</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Current Period Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-balance-sheets-current-period-unaudited-parentheticals</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-statements-of-operations-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Condensed Consolidated Statements of Operations (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-statements-of-operations-unaudited-parentheticals</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Condensed Consolidated Statements of Comprehensive Loss (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-statements-of-comprehensive-loss-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Loss (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-consolidated-statements-of-stockholders-equity-unaudited</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Statement - Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-consolidated-statements-of-stockholders-equity-unaudited-parentheticals</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-condensed-consolidated-statements-of-cash-flows-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 1 - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 2 - Goodwill and Purchased Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets</Role>
      <ShortName>Note 2 - Goodwill and Purchased Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 3 - Borrowings and Credit Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements</Role>
      <ShortName>Note 3 - Borrowings and Credit Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 4 - Restructuring Charges</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges</Role>
      <ShortName>Note 4 - Restructuring Charges</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 6 - Employee Stock Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-6-employee-stock-benefit-plans</Role>
      <ShortName>Note 6 - Employee Stock Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 7 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-7-income-taxes</Role>
      <ShortName>Note 7 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 8 - Segment and Geographic Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-8-segment-and-geographic-information</Role>
      <ShortName>Note 8 - Segment and Geographic Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 9 - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases</Role>
      <ShortName>Note 9 - Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 10 - Discontinued Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations</Role>
      <ShortName>Note 10 - Discontinued Operations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 11 - Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-11-contingencies</Role>
      <ShortName>Note 11 - Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 12 - Guarantees</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-12-guarantees</Role>
      <ShortName>Note 12 - Guarantees</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>021 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-significant-accounting-policies-policies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>022 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-tables</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 2 - Goodwill and Purchased Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets-tables</Role>
      <ShortName>Note 2 - Goodwill and Purchased Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 3 - Borrowings and Credit Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements-tables</Role>
      <ShortName>Note 3 - Borrowings and Credit Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 4 - Restructuring Charges (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges-tables</Role>
      <ShortName>Note 4 - Restructuring Charges (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>026 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-tables</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 8 - Segment and Geographic Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-8-segment-and-geographic-information-tables</Role>
      <ShortName>Note 8 - Segment and Geographic Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-8-segment-and-geographic-information</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>028 - Disclosure - Note 9 - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-tables</Role>
      <ShortName>Note 9 - Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-9-leases</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 10 - Discontinued Operations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations-tables</Role>
      <ShortName>Note 10 - Discontinued Operations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 12 - Guarantees (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-12-guarantees-tables</Role>
      <ShortName>Note 12 - Guarantees (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-12-guarantees</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-details-textual</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-tables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-inventories-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Property, Plant and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-property-plant-and-equipment-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Property, Plant and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-reported-sharebased-compensation-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Computation of Basic and Diluted Income (Loss) Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-computation-of-basic-and-diluted-income-loss-per-share-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Computation of Basic and Diluted Income (Loss) Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-disaggregation-of-revenue-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Customer Concentration (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-1-summary-of-significant-accounting-policies-customer-concentration-details</Role>
      <ShortName>Note 1 - Summary of Significant Accounting Policies - Customer Concentration (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 2 - Goodwill and Purchased Intangible Assets (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets-details-textual</Role>
      <ShortName>Note 2 - Goodwill and Purchased Intangible Assets (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets-tables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 2 - Goodwill and Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets-changes-in-carrying-value-of-goodwill-details</Role>
      <ShortName>Note 2 - Goodwill and Purchased Intangible Assets - Changes in Carrying Value of Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 2 - Goodwill and Purchased Intangible Assets - Purchased Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-2-goodwill-and-purchased-intangible-assets-purchased-intangible-assets-details</Role>
      <ShortName>Note 2 - Goodwill and Purchased Intangible Assets - Purchased Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 3 - Borrowings and Credit Agreements (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements-details-textual</Role>
      <ShortName>Note 3 - Borrowings and Credit Agreements (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements-tables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 3 - Borrowings and Credit Agreements - Summary of Borrowings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-3-borrowings-and-credit-agreements-summary-of-borrowings-details</Role>
      <ShortName>Note 3 - Borrowings and Credit Agreements - Summary of Borrowings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 4 - Restructuring Charges (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges-details-textual</Role>
      <ShortName>Note 4 - Restructuring Charges (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges-tables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 4 - Restructuring Charges - Charges Related to the Wind Down Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-4-restructuring-charges-charges-related-to-the-wind-down-plan-details</Role>
      <ShortName>Note 4 - Restructuring Charges - Charges Related to the Wind Down Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-details-textual</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-tables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-shortterm-investments-by-security-type-details</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value - Short-term Investments by Security Type (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>047 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-effective-maturities-of-shortterm-investments-details</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value - Effective Maturities of Short-term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>048 - Disclosure - Note 5 - Financial Instruments Measured at Fair Value - Assets Measured at Fair Value on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-5-financial-instruments-measured-at-fair-value-assets-measured-at-fair-value-on-recurring-basis-details</Role>
      <ShortName>Note 5 - Financial Instruments Measured at Fair Value - Assets Measured at Fair Value on Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>049 - Disclosure - Note 6 - Employee Stock Benefit Plans (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-6-employee-stock-benefit-plans-details-textual</Role>
      <ShortName>Note 6 - Employee Stock Benefit Plans (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-6-employee-stock-benefit-plans</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>050 - Disclosure - Note 7 - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-7-income-taxes-details-textual</Role>
      <ShortName>Note 7 - Income Taxes (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-7-income-taxes</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>051 - Disclosure - Note 8 - Segment and Geographic Information - Summary of Current Segments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-8-segment-and-geographic-information-summary-of-current-segments-details</Role>
      <ShortName>Note 8 - Segment and Geographic Information - Summary of Current Segments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>052 - Disclosure - Note 9 - Leases (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-details-textual</Role>
      <ShortName>Note 9 - Leases (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-9-leases-tables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>053 - Disclosure - Note 9 - Leases - Balance Sheet Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-balance-sheet-information-details</Role>
      <ShortName>Note 9 - Leases - Balance Sheet Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>054 - Disclosure - Note 9 - Leases - Lease Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-lease-expense-details</Role>
      <ShortName>Note 9 - Leases - Lease Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>055 - Disclosure - Note 9 - Leases - Future Minimum Lease Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-future-minimum-lease-payments-details</Role>
      <ShortName>Note 9 - Leases - Future Minimum Lease Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>056 - Disclosure - Note 9 - Leases - Cash Flow Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-9-leases-cash-flow-information-details</Role>
      <ShortName>Note 9 - Leases - Cash Flow Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>057 - Disclosure - Note 10 - Discontinued Operations (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations-details-textual</Role>
      <ShortName>Note 10 - Discontinued Operations (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations-tables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>058 - Disclosure - Note 10 - Discontinued Operations - Balance Sheet Information for Fixture Services Business (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations-balance-sheet-information-for-fixture-services-business-details</Role>
      <ShortName>Note 10 - Discontinued Operations - Balance Sheet Information for Fixture Services Business (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>059 - Disclosure - Note 10 - Discontinued Operations - Summary of Operating Results (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-10-discontinued-operations-summary-of-operating-results-details</Role>
      <ShortName>Note 10 - Discontinued Operations - Summary of Operating Results (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>060 - Disclosure - Note 12 - Guarantees (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-12-guarantees-details-textual</Role>
      <ShortName>Note 12 - Guarantees (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cohu.com/20200627/role/statement-note-12-guarantees-tables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="cohu20200630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>061 - Disclosure - Note 12 - Guarantees - Changes in Accrued Warranty (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cohu.com/20200627/role/statement-note-12-guarantees-changes-in-accrued-warranty-details</Role>
      <ShortName>Note 12 - Guarantees - Changes in Accrued Warranty (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="cohu20200630_10q.htm">cohu20200630_10q.htm</File>
    <File>cohu-20200627.xsd</File>
    <File>cohu-20200627_cal.xml</File>
    <File>cohu-20200627_def.xml</File>
    <File>cohu-20200627_lab.xml</File>
    <File>cohu-20200627_pre.xml</File>
    <File>ex_196595.htm</File>
    <File>ex_196596.htm</File>
    <File>ex_196597.htm</File>
    <File>ex_196598.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
