<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>255</ContextCount>
  <ElementCount>305</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>52</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>75000 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>75010 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfFinancialCondition</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>75020 - Statement - CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfFinancialConditionParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>75030 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>75040 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>75050 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfChangesInStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>75060 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfChangesInStockholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>75070 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995455 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995475 - Disclosure - Investment Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecurities</Role>
      <ShortName>Investment Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Loans Receivable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivable</Role>
      <ShortName>Loans Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995495 - Disclosure - Deposits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/Deposits</Role>
      <ShortName>Deposits</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995505 - Disclosure - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/Borrowings</Role>
      <ShortName>Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Fair Value Measurements and Disclosures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosures</Role>
      <ShortName>Fair Value Measurements and Disclosures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995525 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995535 - Disclosure - Goodwill and Core Deposit Intangible</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangible</Role>
      <ShortName>Goodwill and Core Deposit Intangible</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Risk and Uncertainties</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/RiskAndUncertainties</Role>
      <ShortName>Risk and Uncertainties</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/EarningsPerShare</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Investment Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecuritiesTables</Role>
      <ShortName>Investment Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecurities</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Loans Receivable (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableTables</Role>
      <ShortName>Loans Receivable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivable</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Deposits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/DepositsTables</Role>
      <ShortName>Deposits (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/Deposits</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Fair Value Measurements and Disclosures (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresTables</Role>
      <ShortName>Fair Value Measurements and Disclosures (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosures</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/Leases</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Goodwill and Core Deposit Intangible (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangibleTables</Role>
      <ShortName>Goodwill and Core Deposit Intangible (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangible</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995645 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995655 - Disclosure - Earnings Per Share - Summary of Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/EarningsPerShareSummaryOfEarningsPerShareDetail</Role>
      <ShortName>Earnings Per Share - Summary of Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995665 - Disclosure - Earnings Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/EarningsPerShareScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareDetail</Role>
      <ShortName>Earnings Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Investment Securities - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecuritiesAdditionalInformationDetail</Role>
      <ShortName>Investment Securities - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995685 - Disclosure - Investment Securities - Summary of Amortized Cost and Estimated Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecuritiesSummaryOfAmortizedCostAndEstimatedFairValueDetail</Role>
      <ShortName>Investment Securities - Summary of Amortized Cost and Estimated Fair Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995695 - Disclosure - Investment Securities - Summary of Fair Value of Available For Sale Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecuritiesSummaryOfFairValueOfAvailableForSaleSecuritiesDetail</Role>
      <ShortName>Investment Securities - Summary of Fair Value of Available For Sale Securities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995705 - Disclosure - Investment Securities - Summary of Securities Available For Sale By Contractual Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/InvestmentSecuritiesSummaryOfSecuritiesAvailableForSaleByContractualMaturityDetail</Role>
      <ShortName>Investment Securities - Summary of Securities Available For Sale By Contractual Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995715 - Disclosure - Loans Receivable - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableAdditionalInformationDetail</Role>
      <ShortName>Loans Receivable - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995725 - Disclosure - Loans Receivable - Summary of Loans Receivable Net (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfLoansReceivableNetDetail</Role>
      <ShortName>Loans Receivable - Summary of Loans Receivable Net (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995735 - Disclosure - Loans Receivable - Summary of components of allowance for credit losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfComponentsOfAllowanceForCreditLossesDetail</Role>
      <ShortName>Loans Receivable - Summary of components of allowance for credit losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995745 - Disclosure - Loans Receivable - Summary of Nonaccrual Loans by Segment of Loan Portfolio (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfNonaccrualLoansBySegmentOfLoanPortfolioDetail</Role>
      <ShortName>Loans Receivable - Summary of Nonaccrual Loans by Segment of Loan Portfolio (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Loans Receivable - Summary of Performance and Credit Quality of Loan Portfolio (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfPerformanceAndCreditQualityOfLoanPortfolioDetail</Role>
      <ShortName>Loans Receivable - Summary of Performance and Credit Quality of Loan Portfolio (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995765 - Disclosure - Loans Receivable - Summary of loans by year of origination, internally assigned credit grades and risk characteristics (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfLoansByYearOfOriginationInternallyAssignedCreditGradesAndRiskCharacteristicsDetail</Role>
      <ShortName>Loans Receivable - Summary of loans by year of origination, internally assigned credit grades and risk characteristics (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Loans Receivable - Summary of Allowance for Loan Losses On Loans Receivables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfAllowanceForLoanLossesOnLoansReceivablesDetail</Role>
      <ShortName>Loans Receivable - Summary of Allowance for Loan Losses On Loans Receivables (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995785 - Disclosure - Loans Receivable - Summary of Allowance for Loan Losses On Loans Receivables (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LoansReceivableSummaryOfAllowanceForLoanLossesOnLoansReceivablesParentheticalDetail</Role>
      <ShortName>Loans Receivable - Summary of Allowance for Loan Losses On Loans Receivables (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995795 - Disclosure - Deposits - Summary of Components of Deposits (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/DepositsSummaryOfComponentsOfDepositsDetail</Role>
      <ShortName>Deposits - Summary of Components of Deposits (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Borrowings - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/BorrowingsAdditionalInformationDetail</Role>
      <ShortName>Borrowings - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Fair Value Measurements and Disclosures - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresSummaryOfFinancialAssetsMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements and Disclosures - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Fair Value Measurements and Disclosures - Summary of Financial Assets Measured at Fair Value on NonRecurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresSummaryOfFinancialAssetsMeasuredAtFairValueOnNonrecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements and Disclosures - Summary of Financial Assets Measured at Fair Value on NonRecurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995845 - Disclosure - Fair Value Measurements and Disclosures - Summary of Quantitative Information Using Level 3 Fair Value Measurements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresSummaryOfQuantitativeInformationUsingLevel3FairValueMeasurementsDetail</Role>
      <ShortName>Fair Value Measurements and Disclosures - Summary of Quantitative Information Using Level 3 Fair Value Measurements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995855 - Disclosure - Fair Value Measurements and Disclosures - Summary of Carrying Amounts and Estimated Fair Value of Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresSummaryOfCarryingAmountsAndEstimatedFairValueOfFinancialInstrumentsDetail</Role>
      <ShortName>Fair Value Measurements and Disclosures - Summary of Carrying Amounts and Estimated Fair Value of Financial Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995865 - Disclosure - Fair Value Measurements and Disclosures - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/FairValueMeasurementsAndDisclosuresAdditionalInformationDetail</Role>
      <ShortName>Fair Value Measurements and Disclosures - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995875 - Disclosure - Leases - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LeasesAdditionalInformationDetail</Role>
      <ShortName>Leases - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995885 - Disclosure - Leases - Summary of Operating Leases of Lessee (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LeasesSummaryOfOperatingLeasesOfLesseeDetail</Role>
      <ShortName>Leases - Summary of Operating Leases of Lessee (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995895 - Disclosure - Leases - Summary of Lessee Operating Lease Liability Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LeasesSummaryOfLesseeOperatingLeaseLiabilityMaturityDetail</Role>
      <ShortName>Leases - Summary of Lessee Operating Lease Liability Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>995915 - Disclosure - Leases - Summary of Lease Cost (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/LeasesSummaryOfLeaseCostDetail</Role>
      <ShortName>Leases - Summary of Lease Cost (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>995925 - Disclosure - Goodwill and Core Deposit Intangible - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangibleAdditionalInformationDetail</Role>
      <ShortName>Goodwill and Core Deposit Intangible - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>995935 - Disclosure - Goodwill and Core Deposit Intangible - Summary of Carrying Amount of Goodwill and Core Deposit Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangibleSummaryOfCarryingAmountOfGoodwillAndCoreDepositIntangibleAssetsDetail</Role>
      <ShortName>Goodwill and Core Deposit Intangible - Summary of Carrying Amount of Goodwill and Core Deposit Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>995945 - Disclosure - Goodwill and Core Deposit Intangible - Summary of Future Fiscal Periods Amortization for the Core Deposit Intangible (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/GoodwillAndCoreDepositIntangibleSummaryOfFutureFiscalPeriodsAmortizationForTheCoreDepositIntangibleDetail</Role>
      <ShortName>Goodwill and Core Deposit Intangible - Summary of Future Fiscal Periods Amortization for the Core Deposit Intangible (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="bprn-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>995955 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://thebankofprinceton.com/20260331/taxonomy/role/SubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="bprn-20260331.htm">bprn-20260331.htm</File>
    <File>bprn-20260331.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1142">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="31">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
