<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.1.9</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>164</ContextCount>
  <ElementCount>277</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>52</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>10</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/CondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002501 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Nature of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NatureOfOperations</Role>
      <ShortName>Nature of Operations</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Basis of Financial Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BasisOfFinancialReporting</Role>
      <ShortName>Basis of Financial Reporting</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Net Income Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NetIncomePerShare</Role>
      <ShortName>Net Income Per Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Business Combinations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinations</Role>
      <ShortName>Business Combinations</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Goodwill</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/Goodwill</Role>
      <ShortName>Goodwill</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Amortizable Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/AmortizableIntangibleAssets</Role>
      <ShortName>Amortizable Intangible Assets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SupplementalDisclosuresOfCashFlowInformationAndNonCashFinancingAndInvestingActivities</Role>
      <ShortName>Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Legal and Regulatory Proceedings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LegalAndRegulatoryProceedings</Role>
      <ShortName>Legal and Regulatory Proceedings</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/Investments</Role>
      <ShortName>Investments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Losses and Loss Adjustment Reserve</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LossesAndLossAdjustmentReserve</Role>
      <ShortName>Losses and Loss Adjustment Reserve</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Statutory Financial Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/StatutoryFinancialInformation</Role>
      <ShortName>Statutory Financial Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Subsidiary Dividend Restrictions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SubsidiaryDividendRestrictions</Role>
      <ShortName>Subsidiary Dividend Restrictions</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/ShareholdersEquity</Role>
      <ShortName>Shareholders' Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Nature of Operations (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NatureOfOperationsPolicies</Role>
      <ShortName>Nature of Operations (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Net Income Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NetIncomePerShareTables</Role>
      <ShortName>Net Income Per Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Business Combinations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsTables</Role>
      <ShortName>Business Combinations (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Goodwill (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/GoodwillTables</Role>
      <ShortName>Goodwill (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Amortizable Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/AmortizableIntangibleAssetsTables</Role>
      <ShortName>Amortizable Intangible Assets (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Long-Term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LongTermDebtTables</Role>
      <ShortName>Long-Term Debt (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SupplementalDisclosuresOfCashFlowInformationAndNonCashFinancingAndInvestingActivitiesTables</Role>
      <ShortName>Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/InvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Losses and Loss Adjustment Reserve (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LossesAndLossAdjustmentReserveTables</Role>
      <ShortName>Losses and Loss Adjustment Reserve (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Nature of Operations - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NatureOfOperationsAdditionalInformationDetail</Role>
      <ShortName>Nature of Operations - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Net Income Per Share - Reconciliation between Basic and Diluted Weighted Average Shares Outstanding (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/NetIncomePerShareReconciliationBetweenBasicAndDilutedWeightedAverageSharesOutstandingDetail</Role>
      <ShortName>Net Income Per Share - Reconciliation between Basic and Diluted Weighted Average Shares Outstanding (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Business Combinations - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsAdditionalInformationDetail</Role>
      <ShortName>Business Combinations - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Business Combinations - Acquisitions Accounted for Business Combinations (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsAcquisitionsAccountedForBusinessCombinationsDetail</Role>
      <ShortName>Business Combinations - Acquisitions Accounted for Business Combinations (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsEstimatedFairValuesOfAggregateAssetsAndLiabilitiesAcquiredDetail</Role>
      <ShortName>Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2404405 - Disclosure - Business Combinations - Results of Operations (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsResultsOfOperationsDetail</Role>
      <ShortName>Business Combinations - Results of Operations (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2404406 - Disclosure - Business Combinations - Additions, Payments, and Net Changes, as well as Interest Expense Accretion on Estimated Acquisition Earn-Out Payables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/BusinessCombinationsAdditionsPaymentsAndNetChangesAsWellAsInterestExpenseAccretionOnEstimatedAcquisitionEarnOutPayablesDetail</Role>
      <ShortName>Business Combinations - Additions, Payments, and Net Changes, as well as Interest Expense Accretion on Estimated Acquisition Earn-Out Payables (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Goodwill - Changes in Carrying Value of Goodwill by Operating Segment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/GoodwillChangesInCarryingValueOfGoodwillByOperatingSegmentDetail</Role>
      <ShortName>Goodwill - Changes in Carrying Value of Goodwill by Operating Segment (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Amortizable Intangible Assets - Amortizable Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/AmortizableIntangibleAssetsAmortizableIntangibleAssetsDetail</Role>
      <ShortName>Amortizable Intangible Assets - Amortizable Intangible Assets (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - Amortizable Intangible Assets - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/AmortizableIntangibleAssetsAdditionalInformationDetail</Role>
      <ShortName>Amortizable Intangible Assets - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Long-Term Debt - Long-Term Debt Instrument (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LongTermDebtLongTermDebtInstrumentDetail</Role>
      <ShortName>Long-Term Debt - Long-Term Debt Instrument (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Long-Term Debt - Long-Term Debt Instrument (Additional Information) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LongTermDebtLongTermDebtInstrumentAdditionalInformationDetail</Role>
      <ShortName>Long-Term Debt - Long-Term Debt Instrument (Additional Information) (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - Long-Term Debt - Narrative (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LongTermDebtNarrativeDetail</Role>
      <ShortName>Long-Term Debt - Narrative (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Significant Non-Cash Investing and Financing Activities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SupplementalDisclosuresOfCashFlowInformationAndNonCashFinancingAndInvestingActivitiesSignificantNonCashInvestingAndFinancingActivitiesDetail</Role>
      <ShortName>Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Significant Non-Cash Investing and Financing Activities (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Segment Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SegmentInformationAdditionalInformationDetail</Role>
      <ShortName>Segment Information - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Segment Information - Summarized Financial Information Reportable Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SegmentInformationSummarizedFinancialInformationReportableSegmentsDetail</Role>
      <ShortName>Segment Information - Summarized Financial Information Reportable Segments (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Investments - Schedule of Investments in Fixed Maturity Securities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/InvestmentsScheduleOfInvestmentsInFixedMaturitySecuritiesDetail</Role>
      <ShortName>Investments - Schedule of Investments in Fixed Maturity Securities (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Investments - Summary of Unrealized Loss Position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/InvestmentsSummaryOfUnrealizedLossPositionDetail</Role>
      <ShortName>Investments - Summary of Unrealized Loss Position (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/InvestmentsAdditionalInformationDetail</Role>
      <ShortName>Investments - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2411405 - Disclosure - Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/InvestmentsAmortizedCostAndFairValueOfFixedMaturitySecuritiesByContractualMaturityDetail</Role>
      <ShortName>Investments - Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Losses and Loss Adjustment Reserve - Effects of Reinsurance on Premiums Written and Earned (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LossesAndLossAdjustmentReserveEffectsOfReinsuranceOnPremiumsWrittenAndEarnedDetail</Role>
      <ShortName>Losses and Loss Adjustment Reserve - Effects of Reinsurance on Premiums Written and Earned (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2412403 - Disclosure - Losses and Loss Adjustment Reserve - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/LossesAndLossAdjustmentReserveAdditionalInformationDetail</Role>
      <ShortName>Losses and Loss Adjustment Reserve - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2413401 - Disclosure - Statutory Financial Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/StatutoryFinancialInformationAdditionalInformationDetail</Role>
      <ShortName>Statutory Financial Information - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2414401 - Disclosure - Subsidiary Dividend Restrictions - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/SubsidiaryDividendRestrictionsAdditionalInformationDetail</Role>
      <ShortName>Subsidiary Dividend Restrictions - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2415401 - Disclosure - Shareholders' Equity - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.bbinsurance.com/role/ShareholdersEquityAdditionalInformationDetail</Role>
      <ShortName>Shareholders' Equity - Additional Information (Detail)</ShortName>
    </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">Element bro_BusinessAcquisitionEarnOutPayables had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_CededPremiumsWritten had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_DebtInstrumentInterestRateStatedPercentage had a mix of decimals attribute values: 0 5.</Log>
    <Log type="Info">Element us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_LongTermDebt had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_PaymentsToAcquireBusinessesGross had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ReinsuranceRecoverablesOnUnpaidLosses had a mix of decimals attribute values: -5 0.</Log>
    <Log type="Info">Element us-gaap_Revenues had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_TreasuryStockShares had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_TreasuryStockValue had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">'Monetary' elements on report '2407402 - Disclosure - Long-Term Debt - Long-Term Debt Instrument (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2411404 - Disclosure - Investments - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2412403 - Disclosure - Losses and Loss Adjustment Reserve - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)</Log>
  </Logs>
  <InputFiles>
    <File>bro-20150331.xml</File>
    <File>bro-20150331.xsd</File>
    <File>bro-20150331_cal.xml</File>
    <File>bro-20150331_def.xml</File>
    <File>bro-20150331_lab.xml</File>
    <File>bro-20150331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
