<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>378</ContextCount>
  <ElementCount>396</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>89</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-balance-sheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated Balance Sheets (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-balance-sheets-parentheticals</Role>
      <ShortName>Consolidated Balance Sheets (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Consolidated Statements of Operations and Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-statements-of-operations-and-comprehensive-income</Role>
      <ShortName>Consolidated Statements of Operations and Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Consolidated Statements of Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-statements-of-shareholders-equity</Role>
      <ShortName>Consolidated Statements of Shareholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Consolidated Statements of Shareholders' Equity (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-statements-of-shareholders-equity-parentheticals</Role>
      <ShortName>Consolidated Statements of Shareholders' Equity (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-consolidated-statements-of-cash-flows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Disclosure - Note 1 - General</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-1-general</Role>
      <ShortName>Note 1 - General</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Note 2 - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-2-summary-of-significant-accounting-policies</Role>
      <ShortName>Note 2 - Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 3 - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-3-fair-value-measurements</Role>
      <ShortName>Note 3 - Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 4 - Cash and Cash Equivalents</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-4-cash-and-cash-equivalents</Role>
      <ShortName>Note 4 - Cash and Cash Equivalents</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 5 - Short-term Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-5-shortterm-investments</Role>
      <ShortName>Note 5 - Short-term Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 6 - Inventories</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-6-inventories</Role>
      <ShortName>Note 6 - Inventories</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-7-prepaid-expenses-and-other-current-assets</Role>
      <ShortName>Note 7 - Prepaid Expenses and Other Current Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 8 - Long-term Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments</Role>
      <ShortName>Note 8 - Long-term Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 9 - Property and Equipment, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net</Role>
      <ShortName>Note 9 - Property and Equipment, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 10 - Other Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-10-other-assets</Role>
      <ShortName>Note 10 - Other Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 11 - Accrued Expenses and Other Current Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-11-accrued-expenses-and-other-current-liabilities</Role>
      <ShortName>Note 11 - Accrued Expenses and Other Current Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 12 - Income Tax</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax</Role>
      <ShortName>Note 12 - Income Tax</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 13 - Retirement and Pension Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans</Role>
      <ShortName>Note 13 - Retirement and Pension Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>020 - Disclosure - Note 14 - Stock-based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation</Role>
      <ShortName>Note 14 - Stock-based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>021 - Disclosure - Note 15 - Earnings (Loss) Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share</Role>
      <ShortName>Note 15 - Earnings (Loss) Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>022 - Disclosure - Note 16 - Commitments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-16-commitments</Role>
      <ShortName>Note 16 - Commitments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 17 - Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-17-contingencies</Role>
      <ShortName>Note 17 - Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 18 - Financial instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-18-financial-instruments</Role>
      <ShortName>Note 18 - Financial instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 19 - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information</Role>
      <ShortName>Note 19 - Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>026 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-significant-accounting-policies-policies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-2-summary-of-significant-accounting-policies</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 3 - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-3-fair-value-measurements-tables</Role>
      <ShortName>Note 3 - Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-3-fair-value-measurements</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>028 - Disclosure - Note 4 - Cash and Cash Equivalents (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-4-cash-and-cash-equivalents-tables</Role>
      <ShortName>Note 4 - Cash and Cash Equivalents (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-4-cash-and-cash-equivalents</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 5 - Short-term Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-5-shortterm-investments-tables</Role>
      <ShortName>Note 5 - Short-term Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-5-shortterm-investments</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 6 - Inventories (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-6-inventories-tables</Role>
      <ShortName>Note 6 - Inventories (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-6-inventories</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-7-prepaid-expenses-and-other-current-assets-tables</Role>
      <ShortName>Note 7 - Prepaid Expenses and Other Current Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-7-prepaid-expenses-and-other-current-assets</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 8 - Long-term Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments-tables</Role>
      <ShortName>Note 8 - Long-term Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 9 - Property and Equipment, Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net-tables</Role>
      <ShortName>Note 9 - Property and Equipment, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 10 - Other Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-10-other-assets-tables</Role>
      <ShortName>Note 10 - Other Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-10-other-assets</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 11 - Accrued Expenses and Other Current Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-11-accrued-expenses-and-other-current-liabilities-tables</Role>
      <ShortName>Note 11 - Accrued Expenses and Other Current Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-11-accrued-expenses-and-other-current-liabilities</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 12 - Income Tax (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-tables</Role>
      <ShortName>Note 12 - Income Tax (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-12-income-tax</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 13 - Retirement and Pension Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-tables</Role>
      <ShortName>Note 13 - Retirement and Pension Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 14 - Stock-based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-tables</Role>
      <ShortName>Note 14 - Stock-based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 15 - Earnings (Loss) Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share-tables</Role>
      <ShortName>Note 15 - Earnings (Loss) Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 16 - Commitments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-16-commitments-tables</Role>
      <ShortName>Note 16 - Commitments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-16-commitments</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 18 - Financial instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-18-financial-instruments-tables</Role>
      <ShortName>Note 18 - Financial instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-18-financial-instruments</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 19 - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-tables</Role>
      <ShortName>Note 19 - Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-19-segment-information</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 2 - Summary of Significant Accounting Policies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-2-summary-of-significant-accounting-policies-details-textual</Role>
      <ShortName>Note 2 - Summary of Significant Accounting Policies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 3 - Fair Value Measurements - Items Measured at Fair Value on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-3-fair-value-measurements-items-measured-at-fair-value-on-a-recurring-basis-details</Role>
      <ShortName>Note 3 - Fair Value Measurements - Items Measured at Fair Value on a Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 3 - Fair Value Measurements - Items Measured at Fair Value on a Nonrecurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-3-fair-value-measurements-items-measured-at-fair-value-on-a-nonrecurring-basis-details</Role>
      <ShortName>Note 3 - Fair Value Measurements - Items Measured at Fair Value on a Nonrecurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 4 - Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-4-cash-and-cash-equivalents-summary-of-cash-and-cash-equivalents-details</Role>
      <ShortName>Note 4 - Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>047 - Disclosure - Note 5 - Short-term Investments - Summary of Short-term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-5-shortterm-investments-summary-of-shortterm-investments-details</Role>
      <ShortName>Note 5 - Short-term Investments - Summary of Short-term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>048 - Disclosure - Note 5 - Short-term Investments - Summary of Short-term Investments by Contractual Maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-5-shortterm-investments-summary-of-shortterm-investments-by-contractual-maturity-details</Role>
      <ShortName>Note 5 - Short-term Investments - Summary of Short-term Investments by Contractual Maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>049 - Disclosure - Note 6 - Inventories - Summary of Inventory (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-6-inventories-summary-of-inventory-details</Role>
      <ShortName>Note 6 - Inventories - Summary of Inventory (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>050 - Disclosure - Note 6 - Inventories - Provisions for Obsolete Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-6-inventories-provisions-for-obsolete-inventories-details</Role>
      <ShortName>Note 6 - Inventories - Provisions for Obsolete Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>051 - Disclosure - Note 7 - Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-7-prepaid-expenses-and-other-current-assets-summary-of-prepaid-expenses-and-other-current-assets-details</Role>
      <ShortName>Note 7 - Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and Other Current Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>052 - Disclosure - Note 8 - Long-term Investments (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments-details-textual</Role>
      <ShortName>Note 8 - Long-term Investments (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments-tables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>053 - Disclosure - Note 8 - Long-term Investments - Long-term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments-longterm-investments-details</Role>
      <ShortName>Note 8 - Long-term Investments - Long-term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>054 - Disclosure - Note 8 - Long-term Investments - Gross Unrealized Gains and Loss of Available-for-sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-8-longterm-investments-gross-unrealized-gains-and-loss-of-availableforsale-securities-details</Role>
      <ShortName>Note 8 - Long-term Investments - Gross Unrealized Gains and Loss of Available-for-sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>055 - Disclosure - Note 9 - Property and Equipment, Net (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net-details-textual</Role>
      <ShortName>Note 9 - Property and Equipment, Net (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net-tables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>056 - Disclosure - Note 9 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-9-property-and-equipment-net-summary-of-property-and-equipment-net-details</Role>
      <ShortName>Note 9 - Property and Equipment, Net - Summary of Property and Equipment, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>057 - Disclosure - Note 10 - Other Assets (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-10-other-assets-details-textual</Role>
      <ShortName>Note 10 - Other Assets (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-10-other-assets-tables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>058 - Disclosure - Note 10 - Other Assets - Summary of Other Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-10-other-assets-summary-of-other-assets-details</Role>
      <ShortName>Note 10 - Other Assets - Summary of Other Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>059 - Disclosure - Note 11 - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-11-accrued-expenses-and-other-current-liabilities-summary-of-accrued-expenses-and-other-current-liabilities-details</Role>
      <ShortName>Note 11 - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>060 - Disclosure - Note 12 - Income Tax (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-details-textual</Role>
      <ShortName>Note 12 - Income Tax (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-tables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>061 - Disclosure - Note 12 - Income Tax - Summary of Income (Loss) Before Income Taxes From Continuing Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-summary-of-income-loss-before-income-taxes-from-continuing-operations-details</Role>
      <ShortName>Note 12 - Income Tax - Summary of Income (Loss) Before Income Taxes From Continuing Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>062 - Disclosure - Note 12 - Income Tax - Summary of Income Tax Expense From Continuing Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-summary-of-income-tax-expense-from-continuing-operations-details</Role>
      <ShortName>Note 12 - Income Tax - Summary of Income Tax Expense From Continuing Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>063 - Disclosure - Note 12 - Income Tax - Reconciliation Between Statutory Income Tax Rate and the Effective Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-reconciliation-between-statutory-income-tax-rate-and-the-effective-income-tax-rate-details</Role>
      <ShortName>Note 12 - Income Tax - Reconciliation Between Statutory Income Tax Rate and the Effective Income Tax Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>064 - Disclosure - Note 12 - Income Tax - Summary of Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-12-income-tax-summary-of-deferred-tax-assets-and-liabilities-details</Role>
      <ShortName>Note 12 - Income Tax - Summary of Deferred Tax Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>065 - Disclosure - Note 13 - Retirement and Pension Plans (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-details-textual</Role>
      <ShortName>Note 13 - Retirement and Pension Plans (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-tables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>066 - Disclosure - Note 13 - Retirement and Pension Plans - Percentage of Major Category of Plan Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-percentage-of-major-category-of-plan-assets-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Percentage of Major Category of Plan Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>067 - Disclosure - Note 13 - Retirement and Pension Plans - Changes in Projected Benefit Obligation and Plan Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-changes-in-projected-benefit-obligation-and-plan-assets-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Changes in Projected Benefit Obligation and Plan Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>068 - Disclosure - Note 13 - Retirement and Pension Plans - Summary of Net Periodic Benefit Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-summary-of-net-periodic-benefit-cost-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Summary of Net Periodic Benefit Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>069 - Disclosure - Note 13 - Retirement and Pension Plans - Summary of Funded Status of the Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-summary-of-funded-status-of-the-plan-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Summary of Funded Status of the Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>070 - Disclosure - Note 13 - Retirement and Pension Plans - Actuarial Assumptions to Determine Benefit Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-actuarial-assumptions-to-determine-benefit-obligations-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Actuarial Assumptions to Determine Benefit Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>071 - Disclosure - Note 13 - Retirement and Pension Plans - Actuarial Assumptions to Determine the Net Periodic Benefit Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-actuarial-assumptions-to-determine-the-net-periodic-benefit-cost-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Actuarial Assumptions to Determine the Net Periodic Benefit Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>072 - Disclosure - Note 13 - Retirement and Pension Plans - Summary of Estimated Future Benefit Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-13-retirement-and-pension-plans-summary-of-estimated-future-benefit-payments-details</Role>
      <ShortName>Note 13 - Retirement and Pension Plans - Summary of Estimated Future Benefit Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>073 - Disclosure - Note 14 - Stock-based Compensation (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-details-textual</Role>
      <ShortName>Note 14 - Stock-based Compensation (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-tables</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>074 - Disclosure - Note 14 - Stock-based Compensation - Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-stock-option-activity-details</Role>
      <ShortName>Note 14 - Stock-based Compensation - Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>075 - Disclosure - Note 14 - Stock-based Compensation - Options Outstanding and Vested Stock Options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-options-outstanding-and-vested-stock-options-details</Role>
      <ShortName>Note 14 - Stock-based Compensation - Options Outstanding and Vested Stock Options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>076 - Disclosure - Note 14 - Stock-based Compensation - Fair Value Assumptions of Stock Options and ESOP (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-fair-value-assumptions-of-stock-options-and-esop-details</Role>
      <ShortName>Note 14 - Stock-based Compensation - Fair Value Assumptions of Stock Options and ESOP (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>077 - Disclosure - Note 14 - Stock-based Compensation - RSUs Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-rsus-activity-details</Role>
      <ShortName>Note 14 - Stock-based Compensation - RSUs Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>078 - Disclosure - Note 14 - Stock-based Compensation - Ordinary Shares Reserved for Future Issuance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-14-stockbased-compensation-ordinary-shares-reserved-for-future-issuance-details</Role>
      <ShortName>Note 14 - Stock-based Compensation - Ordinary Shares Reserved for Future Issuance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>079 - Disclosure - Note 15 - Earnings (Loss) Per Share (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share-details-textual</Role>
      <ShortName>Note 15 - Earnings (Loss) Per Share (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share-tables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>080 - Disclosure - Note 15 - Earnings (Loss) Per Share - Basic and Diluted Earnings (Loss) Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share-basic-and-diluted-earnings-loss-per-share-details</Role>
      <ShortName>Note 15 - Earnings (Loss) Per Share - Basic and Diluted Earnings (Loss) Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-15-earnings-loss-per-share-tables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>081 - Disclosure - Note 16 - Commitments (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-16-commitments-details-textual</Role>
      <ShortName>Note 16 - Commitments (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-16-commitments-tables</ParentRole>
      <Position>82</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>082 - Disclosure - Note 16 - Commitments - Future Minimum Lease Payments for All Noncancelable Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-16-commitments-future-minimum-lease-payments-for-all-noncancelable-operating-leases-details</Role>
      <ShortName>Note 16 - Commitments - Future Minimum Lease Payments for All Noncancelable Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>083 - Disclosure - Note 16 - Commitments - Purchase Obligations and Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-16-commitments-purchase-obligations-and-commitments-details</Role>
      <ShortName>Note 16 - Commitments - Purchase Obligations and Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>084 - Disclosure - Note 17 - Contingencies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-17-contingencies-details-textual</Role>
      <ShortName>Note 17 - Contingencies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-17-contingencies</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>085 - Disclosure - Note 18 - Financial Instruments - Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-18-financial-instruments-financial-instruments-details</Role>
      <ShortName>Note 18 - Financial Instruments - Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>086 - Disclosure - Note 19 - Segment Information (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-details-textual</Role>
      <ShortName>Note 19 - Segment Information (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-tables</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>087 - Disclosure - Note 19 - Segment Information - Summary of Net Sales to Unaffiliated Customers by Geographic Region (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-summary-of-net-sales-to-unaffiliated-customers-by-geographic-region-details</Role>
      <ShortName>Note 19 - Segment Information - Summary of Net Sales to Unaffiliated Customers by Geographic Region (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>088 - Disclosure - Note 19 - Segment Information - Summary of Net Sales to Unaffiliated Customers by Product Category (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-summary-of-net-sales-to-unaffiliated-customers-by-product-category-details</Role>
      <ShortName>Note 19 - Segment Information - Summary of Net Sales to Unaffiliated Customers by Product Category (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>089 - Disclosure - Note 19 - Segment Information - Percentage of Net Sales to Major Customer (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-percentage-of-net-sales-to-major-customer-details</Role>
      <ShortName>Note 19 - Segment Information - Percentage of Net Sales to Major Customer (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="oiim-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>090 - Disclosure - Note 19 - Segment Information - Summary of Long Lived Assets by Physical Location (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.o2micro.com/20181231/role/statement-note-19-segment-information-summary-of-long-lived-assets-by-physical-location-details</Role>
      <ShortName>Note 19 - Segment Information - Summary of Long Lived Assets by Physical Location (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>oiim-20181231.xml</File>
    <File>oiim-20181231.xsd</File>
    <File>oiim-20181231_cal.xml</File>
    <File>oiim-20181231_def.xml</File>
    <File>oiim-20181231_lab.xml</File>
    <File>oiim-20181231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/invest/2013-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
