<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>212</ContextCount>
  <ElementCount>192</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>68</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="bcmi20230630_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://ir.biminicapital.com/20230630/role/statement-document-and-entity-information</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="bcmi20230630_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://ir.biminicapital.com/20230630/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="bcmi20230630_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://ir.biminicapital.com/20230630/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="bcmi20230630_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://ir.biminicapital.com/20230630/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="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-condensed-consolidated-statements-of-stockholders-equity-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-condensed-consolidated-statements-of-cash-flows-unaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Disclosure - Note 1 - Organization and Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies</Role>
      <ShortName>Note 1 - Organization and Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Disclosure - Note 2 - Advisory Services</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services</Role>
      <ShortName>Note 2 - Advisory Services</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Note 3 - Mortgage-backed Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-3-mortgagebacked-securities</Role>
      <ShortName>Note 3 - Mortgage-backed Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Note 4 - Repurchase Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements</Role>
      <ShortName>Note 4 - Repurchase Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Note 5 - Pledged Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-5-pledged-assets</Role>
      <ShortName>Note 5 - Pledged Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Note 6 - Offsetting Assets And Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-6-offsetting-assets-and-liabilities</Role>
      <ShortName>Note 6 - Offsetting Assets And Liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Note 7 - Long-term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt</Role>
      <ShortName>Note 7 - Long-term Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Note 8 - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-8-common-stock</Role>
      <ShortName>Note 8 - Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Note 9 - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-9-commitments-and-contingencies</Role>
      <ShortName>Note 9 - Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Note 10 - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-10-income-taxes</Role>
      <ShortName>Note 10 - Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Note 11 - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-11-earnings-per-share</Role>
      <ShortName>Note 11 - Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>017 - Disclosure - Note 12 - Fair Value</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value</Role>
      <ShortName>Note 12 - Fair Value</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>018 - Disclosure - Note 13 - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information</Role>
      <ShortName>Note 13 - Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>019 - Disclosure - Note 14 - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-14-related-party-transactions</Role>
      <ShortName>Note 14 - Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>021 - Disclosure - Note 1 - Organization and Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies-tables</Role>
      <ShortName>Note 1 - Organization and Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>022 - Disclosure - Note 2 - Advisory Services (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services-tables</Role>
      <ShortName>Note 2 - Advisory Services (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>023 - Disclosure - Note 3 - Mortgage-backed Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-3-mortgagebacked-securities-tables</Role>
      <ShortName>Note 3 - Mortgage-backed Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-3-mortgagebacked-securities</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>024 - Disclosure - Note 4 - Repurchase Agreements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements-tables</Role>
      <ShortName>Note 4 - Repurchase Agreements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>025 - Disclosure - Note 5 - Pledged Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-5-pledged-assets-tables</Role>
      <ShortName>Note 5 - Pledged Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-5-pledged-assets</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>026 - Disclosure - Note 6 - Offsetting Assets And Liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-6-offsetting-assets-and-liabilities-tables</Role>
      <ShortName>Note 6 - Offsetting Assets And Liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-6-offsetting-assets-and-liabilities</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>027 - Disclosure - Note 7 - Long-term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt-tables</Role>
      <ShortName>Note 7 - Long-term Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>028 - Disclosure - Note 11 - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-11-earnings-per-share-tables</Role>
      <ShortName>Note 11 - Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-11-earnings-per-share</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>029 - Disclosure - Note 12 - Fair Value (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value-tables</Role>
      <ShortName>Note 12 - Fair Value (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>030 - Disclosure - Note 13 - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information-tables</Role>
      <ShortName>Note 13 - Segment Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>031 - Disclosure - Note 1 - Organization and Significant Accounting Policies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies-details-textual</Role>
      <ShortName>Note 1 - Organization and Significant Accounting Policies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies-tables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>032 - Disclosure - Note 1 - Organization and Significant Accounting Policies - Summary of Cash, Cash Equivalents and Restricted Cash (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-1-organization-and-significant-accounting-policies-summary-of-cash-cash-equivalents-and-restricted-cash-details</Role>
      <ShortName>Note 1 - Organization and Significant Accounting Policies - Summary of Cash, Cash Equivalents and Restricted Cash (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>033 - Disclosure - Note 2 - Advisory Services (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services-details-textual</Role>
      <ShortName>Note 2 - Advisory Services (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services-tables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>034 - Disclosure - Note 2 - Advisory Services - Advisory Service Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-2-advisory-services-advisory-service-revenue-details</Role>
      <ShortName>Note 2 - Advisory Services - Advisory Service Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>035 - Disclosure - Note 3 - Mortgage-backed Securities - MBS Portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-3-mortgagebacked-securities-mbs-portfolio-details</Role>
      <ShortName>Note 3 - Mortgage-backed Securities - MBS Portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>036 - Disclosure - Note 3 - Mortgage-backed Securities - Net Gain (Loss) From Sale of MBS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-3-mortgagebacked-securities-net-gain-loss-from-sale-of-mbs-details</Role>
      <ShortName>Note 3 - Mortgage-backed Securities - Net Gain (Loss) From Sale of MBS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>037 - Disclosure - Note 4 - Repurchase Agreements (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements-details-textual</Role>
      <ShortName>Note 4 - Repurchase Agreements (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements-tables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>038 - Disclosure - Note 4 - Repurchase Agreements - Schedule of Repurchase Agreements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-4-repurchase-agreements-schedule-of-repurchase-agreements-details</Role>
      <ShortName>Note 4 - Repurchase Agreements - Schedule of Repurchase Agreements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>039 - Disclosure - Note 5 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-5-pledged-assets-schedule-of-financial-instruments-owned-and-pledged-as-collateral-details</Role>
      <ShortName>Note 5 - Pledged Assets - Schedule of Financial Instruments Owned and Pledged as Collateral (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>040 - Disclosure - Note 5 - Pledged Assets -Schedule of Financial Instruments Pledged as Collateral From Counterparties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-5-pledged-assets-schedule-of-financial-instruments-pledged-as-collateral-from-counterparties-details</Role>
      <ShortName>Note 5 - Pledged Assets -Schedule of Financial Instruments Pledged as Collateral From Counterparties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>041 - Disclosure - Note 6 - Offsetting Assets And Liabilities - Offsetting of Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-6-offsetting-assets-and-liabilities-offsetting-of-liabilities-details</Role>
      <ShortName>Note 6 - Offsetting Assets And Liabilities - Offsetting of Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>042 - Disclosure - Note 7 - Long-term Debt (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt-details-textual</Role>
      <ShortName>Note 7 - Long-term Debt (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt-tables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>043 - Disclosure - Note 7 - Long-term Debt - Schedule of Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt-schedule-of-debt-details</Role>
      <ShortName>Note 7 - Long-term Debt - Schedule of Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>044 - Disclosure - Note 7 - Long-term Debt - Future Scheduled Principal Payments on Long-term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-7-longterm-debt-future-scheduled-principal-payments-on-longterm-debt-details</Role>
      <ShortName>Note 7 - Long-term Debt - Future Scheduled Principal Payments on Long-term Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>045 - Disclosure - Note 8 - Common Stock (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-8-common-stock-details-textual</Role>
      <ShortName>Note 8 - Common Stock (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-8-common-stock</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>046 - Disclosure - Note 9 - Commitments and Contingencies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-9-commitments-and-contingencies-details-textual</Role>
      <ShortName>Note 9 - Commitments and Contingencies (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-9-commitments-and-contingencies</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>047 - Disclosure - Note 10 - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-10-income-taxes-details-textual</Role>
      <ShortName>Note 10 - Income Taxes (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-10-income-taxes</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>048 - Disclosure - Note 11 - Earnings Per Share - Schedule of Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-11-earnings-per-share-schedule-of-earnings-per-share-details</Role>
      <ShortName>Note 11 - Earnings Per Share - Schedule of Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>049 - Disclosure - Note 12 - Fair Value (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value-details-textual</Role>
      <ShortName>Note 12 - Fair Value (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value-tables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>050 - Disclosure - Note 12 - Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-12-fair-value-schedule-of-fair-value-assets-and-liabilities-measured-on-recurring-basis-details</Role>
      <ShortName>Note 12 - Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>051 - Disclosure - Note 13 - Segment Information (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information-details-textual</Role>
      <ShortName>Note 13 - Segment Information (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information-tables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>052 - Disclosure - Note 13 - Segment Information - Schedule of Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information-schedule-of-segment-information-details</Role>
      <ShortName>Note 13 - Segment Information - Schedule of Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>053 - Disclosure - Note 13 - Segment Information - Assets in Each Reportable Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-13-segment-information-assets-in-each-reportable-segment-details</Role>
      <ShortName>Note 13 - Segment Information - Assets in Each Reportable Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="bcmi20230630_10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>054 - Disclosure - Note 14 - Related Party Transactions (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://ir.biminicapital.com/20230630/role/statement-note-14-related-party-transactions-details-textual</Role>
      <ShortName>Note 14 - Related Party Transactions (Details Textual)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://ir.biminicapital.com/20230630/role/statement-note-14-related-party-transactions</ParentRole>
      <Position>54</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 50 fact(s) appearing in ix:hidden were eligible for transformation: bmnm:ManagementAgreementExtensionPeriod, bmnm:MonthlyManagementFeeCalculationMultiplierToPercentageOfEquity, dei:EntityRegistrantName, us-gaap:CommonStockParOrStatedValuePerShare, us-gaap:CommonStockSharesAuthorized, us-gaap:CommonStockSharesIssued, us-gaap:CommonStockSharesOutstanding, us-gaap:ConcentrationRiskPercentage1, us-gaap:DebtInstrumentCarryingAmount, us-gaap:InvestmentOwnedBalanceShares, us-gaap:PreferredStockParOrStatedValuePerShare, us-gaap:PreferredStockSharesAuthorized, us-gaap:PreferredStockSharesIssued, us-gaap:PreferredStockSharesOutstanding, us-gaap:RetainedInterestFairValueDisclosure, us-gaap:StockIssuedDuringPeriodSharesNewIssues -  bcmi20230630_10q.htm 8, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="bcmi20230630_10q.htm">bcmi20230630_10q.htm</File>
    <File>bmnm-20230630.xsd</File>
    <File>bmnm-20230630_cal.xml</File>
    <File>bmnm-20230630_def.xml</File>
    <File>bmnm-20230630_lab.xml</File>
    <File>bmnm-20230630_pre.xml</File>
    <File>ex_531781.htm</File>
    <File>ex_531782.htm</File>
    <File>ex_531783.htm</File>
    <File>ex_531784.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>logosm.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="706">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="28">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
