<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.3.0.814</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>367</ContextCount>
  <ElementCount>332</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>60</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>101 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DocumentandEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>103 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfFinancialPositionUnclassified-DepositBasedOperations</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>104 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfFinancialPositionUnclassified-DepositBasedOperationsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>105 - Statement - Consolidated Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfIncomeInterestBasedRevenue</Role>
      <ShortName>Consolidated Statements of Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>106 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfOtherComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>107 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfOtherComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>108 - Statement - Consolidated Statements of Changes in Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>109 - Statement - Consolidated Statements of Changes in Shareholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements of Changes in Shareholders' Equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>110 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/StatementOfCashFlowsIndirectDepositBasedOperations</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>111 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlock</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>112 - Disclosure - Acquisition of Citizens National Bank of Meyersdale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsBusinessCombinationDisclosureTextBlock</Role>
      <ShortName>Acquisition of Citizens National Bank of Meyersdale</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>113 - Disclosure - Earnings Per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock</Role>
      <ShortName>Earnings Per Common Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>114 - Disclosure - Changes in Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock</Role>
      <ShortName>Changes in Accumulated Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>115 - Disclosure - Investment Securities Available-for-Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock</Role>
      <ShortName>Investment Securities Available-for-Sale</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>116 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsLoansNotesTradeAndOtherReceivablesDisclosureTextBlock</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>117 - Disclosure - Stock Option Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock</Role>
      <ShortName>Stock Option Plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>118 - Disclosure - Financial Instruments with Off Balance Sheet Risk</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueOffBalanceSheetRisksDisclosureTextBlock</Role>
      <ShortName>Financial Instruments with Off Balance Sheet Risk</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>119 - Disclosure - Regulatory Matters and Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsRegulatoryCapitalRequirementsUnderBankingRegulationsTextBlock</Role>
      <ShortName>Regulatory Matters and Shareholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>120 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlock</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>121 - Disclosure - Recent Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock</Role>
      <ShortName>Recent Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>122 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlockPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsSignificantAccountingPoliciesTextBlock</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>123 - Disclosure - Earnings Per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlockTables</Role>
      <ShortName>Earnings Per Common Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>124 - Disclosure - Changes in Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlockTables</Role>
      <ShortName>Changes in Accumulated Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>125 - Disclosure - Investment Securities Available-for-Sale (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlockTables</Role>
      <ShortName>Investment Securities Available-for-Sale (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>126 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsLoansNotesTradeAndOtherReceivablesDisclosureTextBlockTables</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsLoansNotesTradeAndOtherReceivablesDisclosureTextBlock</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>127 - Disclosure - Stock Option Plan (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlockTables</Role>
      <ShortName>Stock Option Plan (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>128 - Disclosure - Financial Instruments with Off Balance Sheet Risk (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueOffBalanceSheetRisksDisclosureTextBlockTables</Role>
      <ShortName>Financial Instruments with Off Balance Sheet Risk (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueOffBalanceSheetRisksDisclosureTextBlock</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>129 - Disclosure - Regulatory Matters and Shareholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsRegulatoryCapitalRequirementsUnderBankingRegulationsTextBlockTables</Role>
      <ShortName>Regulatory Matters and Shareholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsRegulatoryCapitalRequirementsUnderBankingRegulationsTextBlock</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>130 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlockTables</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.fnbmarysville.com/taxonomy/role/NotesToFinancialStatementsFairValueDisclosuresTextBlock</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>131 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformation</Role>
      <ShortName>Summary of Significant Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>132 - Disclosure - Acquisition of Citizens National Bank of Meyersdale - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureAcquisitionOfCitizensNationalBankOfMeyersdaleAdditionalInformation</Role>
      <ShortName>Acquisition of Citizens National Bank of Meyersdale - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>133 - Disclosure - Earnings Per Common Share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureEarningsPerCommonShareAdditionalInformation</Role>
      <ShortName>Earnings Per Common Share - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>134 - Disclosure - Earnings Per Common Share - Computation of Earnings per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureEarningsPerCommonShareComputationOfEarningsPerShare</Role>
      <ShortName>Earnings Per Common Share - Computation of Earnings per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>135 - Disclosure - Changes in Accumulated Other Comprehensive Income - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureChangesInAccumulatedOtherComprehensiveIncomeSummaryOfChangesInBalancesOfEachComponentOfAccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Changes in Accumulated Other Comprehensive Income - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>136 - Disclosure - Investment Securities Available-for-Sale - Summary of Amortized Cost and Estimated Fair Values of Investment Securities Available-for-Sale (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureInvestmentSecuritiesAvailableforSaleSummaryOfAmortizedCostAndEstimatedFairValuesOfInvestmentSecuritiesAvailableforSale</Role>
      <ShortName>Investment Securities Available-for-Sale - Summary of Amortized Cost and Estimated Fair Values of Investment Securities Available-for-Sale (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>137 - Disclosure - Investment Securities Available-for-Sale - Schedule of Amortized Cost and Fair Value of Debt Securities Available-for-Sale, by Contractual Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureInvestmentSecuritiesAvailableforSaleScheduleOfAmortizedCostAndFairValueOfDebtSecuritiesAvailableforSaleByContractualMaturity</Role>
      <ShortName>Investment Securities Available-for-Sale - Schedule of Amortized Cost and Fair Value of Debt Securities Available-for-Sale, by Contractual Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>138 - Disclosure - Investment Securities Available-for-Sale - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureInvestmentSecuritiesAvailableforSaleAdditionalInformation</Role>
      <ShortName>Investment Securities Available-for-Sale - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>139 - Disclosure - Investment Securities Available-for-Sale - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category and Length of Time (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureInvestmentSecuritiesAvailableforSaleScheduleOfSecuritiesWithGrossUnrealizedLossesAggregatedByInvestmentCategoryAndLengthOfTime</Role>
      <ShortName>Investment Securities Available-for-Sale - Schedule of Securities with Gross Unrealized Losses Aggregated by Investment Category and Length of Time (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>140 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Loans Receivable (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesScheduleOfLoansReceivable</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Loans Receivable (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>141 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Aging of Loans Receivable by Loan Portfolio Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesSummaryOfAgingOfLoansReceivableByLoanPortfolioSegments</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Aging of Loans Receivable by Loan Portfolio Segments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>142 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesAdditionalInformation</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>143 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Loans by Loan Portfolio Segments on Nonaccrual Status (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesScheduleOfLoansByLoanPortfolioSegmentsOnNonaccrualStatus</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Loans by Loan Portfolio Segments on Nonaccrual Status (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>144 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Impaired Loans by Loan Portfolio Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesScheduleOfImpairedLoansByLoanPortfolioSegments</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Impaired Loans by Loan Portfolio Segments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>145 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Number of Loans and Recorded Investment in TDRs (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesScheduleOfNumberOfLoansAndRecordedInvestmentInTDRs</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Number of Loans and Recorded Investment in TDRs (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>146 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Loan Portfolio Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesScheduleOfAllowanceForLoanLossesByLoanPortfolioSegments</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Schedule of Allowance for Loan Losses by Loan Portfolio Segments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>147 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Credit Quality Indicators and Total Credit Exposure by Internally Assigned Grades (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesSummaryOfCreditQualityIndicatorsAndTotalCreditExposureByInternallyAssignedGrades</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Credit Quality Indicators and Total Credit Exposure by Internally Assigned Grades (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>148 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Loans Purchased in Union Transaction (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesSummaryOfLoansPurchasedInUnionTransaction</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Loans Purchased in Union Transaction (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>149 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Unpaid Principal Balances and Related Carrying Amounts of Acquired Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesSummaryOfUnpaidPrincipalBalancesAndRelatedCarryingAmountsOfAcquiredLoans</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Unpaid Principal Balances and Related Carrying Amounts of Acquired Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>150 - Disclosure - Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Changes in Accretable Discount Related to Purchased Credit Impaired Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureLoansReceivableCreditQualityForLoansAndTheAllowanceForLoanLossesSummaryOfChangesInAccretableDiscountRelatedToPurchasedCreditImpairedLoans</Role>
      <ShortName>Loans Receivable, Credit Quality for Loans and the Allowance for Loan Losses - Summary of Changes in Accretable Discount Related to Purchased Credit Impaired Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>151 - Disclosure - Stock Option Plan - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureStockOptionPlanAdditionalInformation</Role>
      <ShortName>Stock Option Plan - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>152 - Disclosure - Stock Option Plan - Schedule of Information Pertaining to Options Outstanding (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureStockOptionPlanScheduleOfInformationPertainingToOptionsOutstanding</Role>
      <ShortName>Stock Option Plan - Schedule of Information Pertaining to Options Outstanding (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>153 - Disclosure - Financial Instruments with Off Balance Sheet Risk - Schedule of Bank's Exposure to Credit Loss (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureFinancialInstrumentsWithOffBalanceSheetRiskScheduleOfBanksExposureToCreditLoss</Role>
      <ShortName>Financial Instruments with Off Balance Sheet Risk - Schedule of Bank's Exposure to Credit Loss (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>154 - Disclosure - Regulatory Matters and Shareholders' Equity - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureRegulatoryMattersAndShareholdersEquityAdditionalInformation</Role>
      <ShortName>Regulatory Matters and Shareholders' Equity - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>155 - Disclosure - Regulatory Matters and Shareholders' Equity - Schedule of Bank's Actual Capital Ratios and Minimum Ratios Required for Capital Adequacy Purposes (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureRegulatoryMattersAndShareholdersEquityScheduleOfBanksActualCapitalRatiosAndMinimumRatiosRequiredForCapitalAdequacyPurposes</Role>
      <ShortName>Regulatory Matters and Shareholders' Equity - Schedule of Bank's Actual Capital Ratios and Minimum Ratios Required for Capital Adequacy Purposes (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>156 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments - Financial Assets Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureFairValueMeasurementsAndFairValuesOfFinancialInstrumentsFinancialAssetsMeasuredAtFairValueOnRecurringBasis</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments - Financial Assets Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>157 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureFairValueMeasurementsAndFairValuesOfFinancialInstrumentsAdditionalInformation</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>158 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments - Summary of Assets Measured at Estimated Fair Value on Nonrecurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureFairValueMeasurementsAndFairValuesOfFinancialInstrumentsSummaryOfAssetsMeasuredAtEstimatedFairValueOnNonrecurringBasis</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments - Summary of Assets Measured at Estimated Fair Value on Nonrecurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="rive-20150930.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>159 - Disclosure - Fair Value Measurements and Fair Values of Financial Instruments - Estimated Fair Values of Riverview's Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.fnbmarysville.com/taxonomy/role/DisclosureFairValueMeasurementsAndFairValuesOfFinancialInstrumentsEstimatedFairValuesOfRiverviewsFinancialInstruments</Role>
      <ShortName>Fair Value Measurements and Fair Values of Financial Instruments - Estimated Fair Values of Riverview's Financial Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</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="Info">In ''Consolidated Balance Sheets'', column(s) 2, 4, 5, 6 are contained in other reports, so were removed by flow through suppression.</Log>
    <Log type="Info">In ''Consolidated Statements of Cash Flows'', column(s) 1, 2 are contained in other reports, so were removed by flow through suppression.</Log>
  </Logs>
  <InputFiles>
    <File>rive-20150930.xml</File>
    <File>rive-20150930_cal.xml</File>
    <File>rive-20150930_def.xml</File>
    <File>rive-20150930_lab.xml</File>
    <File>rive-20150930_pre.xml</File>
    <File>rive-20150930.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>

