<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>258</ContextCount>
  <ElementCount>324</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>60</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - Condensed Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedStatementsofOperations</Role>
      <ShortName>Condensed Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - Condensed Consolidated Statements of Comprehensive (Loss) Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedStatementsofComprehensiveLossIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive (Loss) Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Condensed Consolidated Statements of Changes in Stockholders’ Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity</Role>
      <ShortName>Condensed Consolidated Statements of Changes in Stockholders’ Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CondensedConsolidatedStatementsofCashFlows</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Disclosure - Description of Business and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - Financial Statement Components</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FinancialStatementComponents</Role>
      <ShortName>Financial Statement Components</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Property, Plant and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/PropertyPlantandEquipment</Role>
      <ShortName>Property, Plant and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssets</Role>
      <ShortName>Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Revenue and Geographic Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformation</Role>
      <ShortName>Revenue and Geographic Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Stock-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockBasedCompensation</Role>
      <ShortName>Stock-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/SegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Basic Income (Loss) and Diluted Loss per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShare</Role>
      <ShortName>Basic Income (Loss) and Diluted Loss per Common Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.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>22</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Description of Business and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPolicies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/FairValueMeasurements</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Financial Statement Components (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FinancialStatementComponentsTables</Role>
      <ShortName>Financial Statement Components (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/FinancialStatementComponents</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Property, Plant and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/PropertyPlantandEquipmentTables</Role>
      <ShortName>Property, Plant and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/PropertyPlantandEquipment</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsTables</Role>
      <ShortName>Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/GoodwillandIntangibleAssets</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/Leases</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/Debt</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Revenue and Geographic Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformationTables</Role>
      <ShortName>Revenue and Geographic Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/RevenueandGeographicInformation</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/StockholdersEquity</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Stock-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockBasedCompensationTables</Role>
      <ShortName>Stock-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/StockBasedCompensation</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Basic Income (Loss) and Diluted Loss per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShareTables</Role>
      <ShortName>Basic Income (Loss) and Diluted Loss per Common Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShare</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Description of Business and Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesDetails</Role>
      <ShortName>Description of Business and Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/DescriptionofBusinessandSummaryofSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FairValueMeasurementsScheduleofFinancialAssetsMeasuredatFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Fair Value Measurements - Schedule of Contractual Maturities of Marketable Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FairValueMeasurementsScheduleofContractualMaturitiesofMarketableSecuritiesDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Contractual Maturities of Marketable Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Fair Value Measurements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FairValueMeasurementsAdditionalInformationDetails</Role>
      <ShortName>Fair Value Measurements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Financial Statement Components - Schedule of Accounts Receivable, Net of Allowances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FinancialStatementComponentsScheduleofAccountsReceivableNetofAllowancesDetails</Role>
      <ShortName>Financial Statement Components - Schedule of Accounts Receivable, Net of Allowances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Financial Statement Components - Schedule of Components for Expected Credit Losses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FinancialStatementComponentsScheduleofComponentsforExpectedCreditLossesDetails</Role>
      <ShortName>Financial Statement Components - Schedule of Components for Expected Credit Losses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Financial Statement Components - Schedule of Accrued Expenses and Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/FinancialStatementComponentsScheduleofAccruedExpensesandOtherCurrentLiabilitiesDetails</Role>
      <ShortName>Financial Statement Components - Schedule of Accrued Expenses and Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Property, Plant and Equipment - Schedule of Property, Plant and Equipment, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentNetDetails</Role>
      <ShortName>Property, Plant and Equipment - Schedule of Property, Plant and Equipment, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Property, Plant and Equipment - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/PropertyPlantandEquipmentAdditionalInformationDetails</Role>
      <ShortName>Property, Plant and Equipment - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Property, Plant and Equipment - Schedule of Depreciation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/PropertyPlantandEquipmentScheduleofDepreciationExpenseDetails</Role>
      <ShortName>Property, Plant and Equipment - Schedule of Depreciation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsScheduleofChangesinCarryingAmountofGoodwillDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Goodwill and Intangible Assets - Schedule of Intangible Assets, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsScheduleofIntangibleAssetsNetDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Intangible Assets, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Goodwill and Intangible Assets - Schedule of Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsScheduleofAmortizationExpenseDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Goodwill and Intangible Assets - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsAdditionalInformationDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Goodwill and Intangible Assets - Schedule of Future Estimated Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/GoodwillandIntangibleAssetsScheduleofFutureEstimatedAmortizationExpenseDetails</Role>
      <ShortName>Goodwill and Intangible Assets - Schedule of Future Estimated Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/LeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Leases - Schedule of Components of Lease Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/LeasesScheduleofComponentsofLeaseExpenseDetails</Role>
      <ShortName>Leases - Schedule of Components of Lease Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Leases - Schedule of Other Supplemental Information Related to Operating Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/LeasesScheduleofOtherSupplementalInformationRelatedtoOperatingLeasesDetails</Role>
      <ShortName>Leases - Schedule of Other Supplemental Information Related to Operating Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Leases - Schedule of Maturities of Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/LeasesScheduleofMaturitiesofLeaseLiabilitiesDetails</Role>
      <ShortName>Leases - Schedule of Maturities of Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Debt - Revolving Credit Facility (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/DebtRevolvingCreditFacilityDetails</Role>
      <ShortName>Debt - Revolving Credit Facility (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Debt - 2026 Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/Debt2026ConvertibleNotesDetails</Role>
      <ShortName>Debt - 2026 Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Debt - 2028 Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/Debt2028ConvertibleNotesDetails</Role>
      <ShortName>Debt - 2028 Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Debt - 2032 Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/Debt2032ConvertibleNotesDetails</Role>
      <ShortName>Debt - 2032 Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Debt - Other Terms of the Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/DebtOtherTermsoftheConvertibleNotesDetails</Role>
      <ShortName>Debt - Other Terms of the Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Debt - Schedule of Net Carrying Amount of Liability Components of Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/DebtScheduleofNetCarryingAmountofLiabilityComponentsofConvertibleNotesDetails</Role>
      <ShortName>Debt - Schedule of Net Carrying Amount of Liability Components of Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Debt - Schedule of Costs Incurred for Capped Calls Related to Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.bandwidth.com/role/DebtScheduleofCostsIncurredforCappedCallsRelatedtoConvertibleNotesDetails</Role>
      <ShortName>Debt - Schedule of Costs Incurred for Capped Calls Related to Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Revenue and Geographic Information - Schedule of Revenue by Geographic Region (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformationScheduleofRevenuebyGeographicRegionDetails</Role>
      <ShortName>Revenue and Geographic Information - Schedule of Revenue by Geographic Region (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Revenue and Geographic Information - Schedule of Receivables and Contract Liabilities From Contracts with Customers (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformationScheduleofReceivablesandContractLiabilitiesFromContractswithCustomersDetails</Role>
      <ShortName>Revenue and Geographic Information - Schedule of Receivables and Contract Liabilities From Contracts with Customers (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Revenue and Geographic Information - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformationAdditionalInformationDetails</Role>
      <ShortName>Revenue and Geographic Information - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Revenue and Geographic Information - Schedule of Long Lived Assets by Geographic Region (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/RevenueandGeographicInformationScheduleofLongLivedAssetsbyGeographicRegionDetails</Role>
      <ShortName>Revenue and Geographic Information - Schedule of Long Lived Assets by Geographic Region (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Issuance (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockholdersEquityScheduleofReservedSharesofCommonStockforIssuanceDetails</Role>
      <ShortName>Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Issuance (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Stockholders' Equity - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockholdersEquityAdditionalInformationDetails</Role>
      <ShortName>Stockholders' Equity - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Stockholders' Equity - Schedule of Share Repurcase Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockholdersEquityScheduleofShareRepurcaseActivityDetails</Role>
      <ShortName>Stockholders' Equity - Schedule of Share Repurcase Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockBasedCompensationScheduleofRestrictedStockUnitActivityDetails</Role>
      <ShortName>Stock-Based Compensation - Schedule of Restricted Stock Unit Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Stock-Based Compensation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockBasedCompensationAdditionalInformationDetails</Role>
      <ShortName>Stock-Based Compensation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Stock-Based Compensation - Schedule of Total Stock-Based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/StockBasedCompensationScheduleofTotalStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stock-Based Compensation - Schedule of Total Stock-Based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/CommitmentsandContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/CommitmentsandContingencies</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Segment Reporting (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/SegmentReportingDetails</Role>
      <ShortName>Segment Reporting (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/SegmentReporting</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/IncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/IncomeTaxes</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Basic Income (Loss) and Diluted Loss per Common Share - Income (Loss) Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShareIncomeLossPerShareDetails</Role>
      <ShortName>Basic Income (Loss) and Diluted Loss per Common Share - Income (Loss) Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShareTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="band-20260630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Basic Income (Loss) and Diluted Loss per Common Share - Schedule of Anti-dilutive Common Shares Excluded from Calculation of Diluted Net (Loss) Income Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShareScheduleofAntidilutiveCommonSharesExcludedfromCalculationofDilutedNetLossIncomePerCommonShareDetails</Role>
      <ShortName>Basic Income (Loss) and Diluted Loss per Common Share - Schedule of Anti-dilutive Common Shares Excluded from Calculation of Diluted Net (Loss) Income Per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.bandwidth.com/role/BasicIncomeLossandDilutedLossperCommonShareTables</ParentRole>
      <Position>74</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="band-20260630.htm">band-20260630.htm</File>
    <File>band-20260630.xsd</File>
    <File>band-20260630_cal.xml</File>
    <File>band-20260630_def.xml</File>
    <File>band-20260630_lab.xml</File>
    <File>band-20260630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2026</BaseTaxonomy>
    <BaseTaxonomy items="966">http://fasb.org/us-gaap/2026</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2026</BaseTaxonomy>
    <BaseTaxonomy items="25">http://xbrl.sec.gov/ecd/2026</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
