<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.3.a.u2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>331</ContextCount>
  <ElementCount>361</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>50</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedBalanceSheets</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00105 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedBalanceSheetsParentheticals</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00200 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedStatementsOfOperations</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00300 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00400 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS??? EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>00500 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/StatementCondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>10101 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>10201 - Disclosure - Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureRecentAccountingPronouncements</Role>
      <ShortName>Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10301 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10401 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10501 - Disclosure - Cash and Due From Banks</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureCashAndDueFromBanks</Role>
      <ShortName>Cash and Due From Banks</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10601 - Disclosure - Available for Sale Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecurities</Role>
      <ShortName>Available for Sale Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10701 - Disclosure - Loans &amp; Allowance for Loan Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAllowanceForLoanLosses</Role>
      <ShortName>Loans &amp; Allowance for Loan Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>10801 - Disclosure - Loan Servicing</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoanServicing</Role>
      <ShortName>Loan Servicing</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>10901 - Disclosure - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureBorrowings</Role>
      <ShortName>Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>11001 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>11101 - Disclosure - Defined Benefit Pension Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureDefinedBenefitPensionPlan</Role>
      <ShortName>Defined Benefit Pension Plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>11201 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>11301 - Disclosure - Regulatory Capital Requirements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirements</Role>
      <ShortName>Regulatory Capital Requirements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>20102 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>30303 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureEarningsPerShare</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>30403 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstruments</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>30603 - Disclosure - Available for Sale Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesTables</Role>
      <ShortName>Available for Sale Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureAvailableForSaleSecurities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>30703 - Disclosure - Loans and Allowance for Loan Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesTables</Role>
      <ShortName>Loans and Allowance for Loan Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>30903 - Disclosure - Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureBorrowingsTables</Role>
      <ShortName>Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureBorrowings</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>31203 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>31303 - Disclosure - Regulatory Capital Requirements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirementsTables</Role>
      <ShortName>Regulatory Capital Requirements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirements</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>40101 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>40301 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureEarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>40401 - Disclosure - Fair Value of Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstrumentsTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>40402 - Disclosure - Fair Value of Financial Instruments - Fair value on non-recurring basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstrumentsFairValueOnNonRecurringBasisDetails</Role>
      <ShortName>Fair Value of Financial Instruments - Fair value on non-recurring basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>40403 - Disclosure - Fair Value of Financial Instruments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureFairValueOfFinancialInstrumentsAdditionalInformationDetails</Role>
      <ShortName>Fair Value of Financial Instruments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>40501 - Disclosure - Cash and Due From Banks (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureCashAndDueFromBanksDetails</Role>
      <ShortName>Cash and Due From Banks (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureCashAndDueFromBanks</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>40601 - Disclosure - Available for Sale Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Available for Sale Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>40602 - Disclosure - Available for Sale Securities - Company???s available for sale securities portfolio (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesCompanysAvailableForSaleSecuritiesPortfolioDetails</Role>
      <ShortName>Available for Sale Securities - Company???s available for sale securities portfolio (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>40603 - Disclosure - Available for Sale Securities - Amortized cost and fair value of available for sale securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesAmortizedCostAndFairValueOfAvailableForSaleSecuritiesDetails</Role>
      <ShortName>Available for Sale Securities - Amortized cost and fair value of available for sale securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>40604 - Disclosure - Available for Sale Securities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureAvailableForSaleSecuritiesAdditionalInformationDetails</Role>
      <ShortName>Available for Sale Securities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>40701 - Disclosure - Loans and Allowance for Loan Losses - Major classifications (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesMajorClassificationsDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Major classifications (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>40702 - Disclosure - Loans and Allowance for Loan Losses - Non-performing loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesNonPerformingLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Non-performing loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>40703 - Disclosure - Loans and Allowance for Loan Losses - Impaired loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesImpairedLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Impaired loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>40704 - Disclosure - Loans and Allowance for Loan Losses - Risk rating (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesRiskRatingDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Risk rating (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>40705 - Disclosure - Loans and Allowance for Loan Losses - Past due loans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesPastDueLoansDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Past due loans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>40706 - Disclosure - Loans and Allowance for Loan Losses - Changes In Allowance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoansAndAllowanceForLoanLossesChangesInAllowanceDetails</Role>
      <ShortName>Loans and Allowance for Loan Losses - Changes In Allowance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>40801 - Disclosure - Loan Servicing (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureLoanServicingDetails</Role>
      <ShortName>Loan Servicing (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureLoanServicing</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>40901 - Disclosure - Borrowings - Tabular Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureBorrowingsTabularInformationDetails</Role>
      <ShortName>Borrowings - Tabular Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>40902 - Disclosure - Borrowings - Table Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureBorrowingsTableNarrativeDetails</Role>
      <ShortName>Borrowings - Table Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>40903 - Disclosure - Borrowings - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureBorrowingsAdditionalInformationDetails</Role>
      <ShortName>Borrowings - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>41001 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureIncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>41101 - Disclosure - Defined Benefit Pension Plan - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureDefinedBenefitPensionPlanAdditionalInformationDetails</Role>
      <ShortName>Defined Benefit Pension Plan - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>41201 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureCommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>41301 - Disclosure - Regulatory Capital Requirements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirementsDetails</Role>
      <ShortName>Regulatory Capital Requirements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirementsTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="tbba-20191231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>41302 - Disclosure - Regulatory Capital Requirements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.tbba.com/role/DisclosureRegulatoryCapitalRequirementsAdditionalInformationDetails</Role>
      <ShortName>Regulatory Capital Requirements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>tbba-20191231.xml</File>
    <File>tbba-20191231.xsd</File>
    <File>tbba-20191231_cal.xml</File>
    <File>tbba-20191231_def.xml</File>
    <File>tbba-20191231_lab.xml</File>
    <File>tbba-20191231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
