Business Combinations [Abstract] Purchase price allocation for current year acquisitions and adjustments made for prior year acquisitions Schedule of Business Acquisitions, by Acquisition [Table Text Block] Estimated fair values of aggregate assets and liabilities acquired Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Unaudited pro forma results Business Acquisition, Pro Forma Information [Table Text Block] Schedule Of Business Acquisition Estimated Earn Out Payables Table [Text Block] Schedule Of Business Acquisition Estimated Earn Out Payables Table [Text Block] Schedule Of Business Acquisition Estimated Earn-Out Payables. Document And Entity Information [Abstract] Document and Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Employee Stock [Member] Employee Stock [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Stock Incentive Plan [Member] Stock Incentive Plan [Member] Stock Incentive Plan [Member] PerformanceStock​Plan [Member] PerformanceStock​Plan [Member] PerformanceStock​Plan [Member] Incentive Stock Option Plan [Member] Incentive Stock Option Plan [Member] Incentive Stock Option Plan [Member] Award Date [Axis] Award Date [Axis] Award Date [Domain] Award Date [Domain] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Share-based Compensation Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table] Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table] 2010 Stock Incentive Plan [Axis] 2010 Stock Incentive Plan [Axis] 2010 Stock Incentive Plan [Axis] 2010 Stock Incentive Plan [Domain] 2010 Stock Incentive Plan [Domain] [Domain] for 2010 Stock Incentive Plan [Axis] Perfomance Based [Member] Perfomance Based [Member] Perfomance Based [Member] Minimum [Member] Minimum [Member] Exercise Price Range [Axis] Exercise Price Range [Axis] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Not​Yet​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Not​Yet​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Not​Yet​Awarded​InPeriod Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Shares​Available​For​Issuance​Under​Stock​Incentive​Plan Shares​Available​For​Issuance​Under​Stock​Incentive​Plan Shares​Available​For​Issuance​Under​Stock​Incentive​Plan Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Granted​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Granted​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Granted​Shares​Outstanding​Number Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Shares​Not​Yet​Awarded​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Shares​Not​Yet​Awarded​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Shares​Not​Yet​Awarded​Outstanding​Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​Not​Yet​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​Not​Yet​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​Not​Yet​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Options​Vesting​Period Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Options​Vesting​Period Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Options​Vesting​Period Stock Issued During Period, Shares, Share-based Compensation, Gross Stock Issued During Period, Shares, Share-based Compensation, Gross Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Short-term Debt [Member] Short-term Debt [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Short-term Investments Short-term Investments Number of securities in unrealized loss position Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions Proceeds from sale of investment in fixed maturity securities Proceeds from Sale and Maturity of Available-for-sale Securities Money Market Funds, at Carrying Value Money Market Funds, at Carrying Value Investments on deposit with the state insurance department Assets Held by Insurance Regulators Time Deposits Time Deposits Earnings Per Share [Abstract] Net Income Per Share Earnings Per Share [Text Block] Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Threshold​Period​Worked​Per​Week​ByEmployees Threshold​Period​Worked​Per​Week​ByEmployees Threshold​Period​Worked​Per​Week​ByEmployees Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Allotted​Value​Maximum Allotted​Value​Maximum Allotted​Value​Maximum Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Beginning Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Beginning Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Beginning Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Ending Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Ending Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Subscription​Period​Ending Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Percent​OfMarket​Price Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Percent​OfMarket​Price Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Percent​OfMarket​Price Value​OfOne​Year​Stock​Option​Percentage Value​OfOne​Year​Stock​Option​Percentage Value​OfOne​Year​Stock​Option​Percentage Estimated​Fair​Value​Per​Share​Option Estimated​Fair​Value​Per​Share​Option Estimated​Fair​Value​Per​Share​Option Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Price​Per​Share Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Price​Per​Share Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Shares​Issued​Aggregate​Purchase​Price​Per​Share Shares held in Employee Stock Option Plan, Suspense Shares Shares held in Employee Stock Option Plan, Suspense Shares Cash​Received​From​Proceeds​ByParticipants Cash​Received​From​Proceeds​ByParticipants Cash​Received​From​Proceeds​ByParticipants Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Equity [Abstract] Shareholders' Equity Stockholders' Equity Note Disclosure [Text Block] Supplemental Cash Flow Elements [Abstract] Schedule of Restricted Cash and Cash Equivalents [Table] Schedule of Restricted Cash and Cash Equivalents [Table] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents inclusive of Restricted Cash [Member] Cash and Cash Equivalents inclusive of Restricted Cash [Member] Cash and Cash Equivalents inclusive of Restricted Cash [Member] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents Restricted Cash and Cash Equivalents Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents, at Carrying Value Cash paid during the period for: Interest Paid [Abstract] Interest Interest Paid Income taxes Income Taxes Paid Significant non-cash investing and financing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Other payables issued for purchased customer accounts Other Payables Obligations of a business that arise from the acquisition of merchandise, materials, supplies and services used in the production and/or sale of goods and services not classified as Trade Payables. Estimated acquisition earn-out payables and related charges Recorded Earn Out Payable Recorded Earn-out Payable Notes Assumed Notes Assumed Notes received on the sale of fixed assets and customer accounts Notes Receivable On Sale Of Fixed Assets And Customer Accounts Notes Receivable on the Sale of Fixed Assets and Customer Accounts Statement of Stockholders' Equity [Abstract] Common Stock, Dividends, Per Share, Cash Paid Common Stock, Dividends, Per Share, Cash Paid Debt Disclosure [Abstract] Long-Term Debt Debt Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Entity by Location [Axis] Entity by Location [Axis] Location [Domain] Location [Domain] London, Bermuda and Cayman Islands London Bermuda And Cayman Islands Operations [Member] London Bermuda and Cayman Islands operations. Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of reportable segments Number of Reportable Segments Total revenues Revenues Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Services Services [Member] Services [Member] Wholesale Brokerage [Member] Wholesale Brokerage [Member] Wholesale Brokerage [Member] Various [Member] Various [Member] Various [member] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Social Security Advocates for the Disabled LLC [Member] Social Security Advocates for the Disabled LLC [Member] Social Security Advocates for the Disabled LLC [Member] Morstan General Agency, Inc [Member] Morstan General Agency, Inc [Member] Morstan General Agency, Inc [Member] Other Acquisitions [Member] Other Acquisitions [Member] Other Acquisitions [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Business Acquisition [Line Items] Business Acquisition [Line Items] Business Acquisition Cost- Note Payable Business Acquisition Cost- Note Payable Business Acquisition Cost- Note Payable Beginning balance Business Acquisition Earn Out Payables Business acquisition earn out payables. Additions to estimated acquisition earn-out payables Additions To Estimated Acquisition Earn Out Payables Additions to estimated acquisition earn out payables. Payments for estimated acquisition earn-out payables Payments For Estimated Acquisition Earn Out Payables Payments for estimated acquisition earn out payables. Subtotal Business Acquisition Earn Out Payable After Change In Additions And Payments Business Acquisition Earn Out Payable After Change In Additions And Payments Net change in earnings from estimated acquisition earn-out payables: Net Change in Earnings from Estimated Acquisition Earn-out Payables [Abstract] Net Change in Earnings from Estimated Acquisition Earn-out Payables [Abstract] Change in fair value on estimated acquisition earn-out payables Change In Fair Value Estimated Acquisition Earn Out Payables Change In Fair Value Estimated Acquisition Earn Out Payables. Interest expense accretion Asset Retirement Obligation, Accretion Expense Net change in earnings from estimated acquisition earn-out payables Change In Estimated Acquisition Earn Out Payable Change In Estimated Acquisition Earn Out Payable Ending balance Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Financial Information [Table Text Block] Quarterly Financial Information [Table Text Block] Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract] Dividend Restrictions [Table] Dividend Restrictions [Table] Dividend Restrictions [Table] Subsegments [Axis] Subsegments [Axis] Subsegments [Domain] Subsegments [Domain] Wright Flood Wright National Flood Insurance Company [Member] Wright National Flood Insurance Company [Member] Maximum Maximum [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Dividend Restrictions [Line Items] Dividend Restrictions [Line Items] [Line Items] for Dividend Restrictions [Table] Dividend rate as a percentage of net income Fair Value Assumptions, Expected Dividend Rate Maximum dividend payout that may be made without prior approval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Statutory Dividend Payment Restrictions Disclosure Statutory Dividend Payment Restrictions Disclosure Goodwill and Intangible Assets Disclosure [Abstract] Changes in Carrying Value of Goodwill by Operating Segment Schedule of Goodwill [Table Text Block] Proceeds from Sale, Maturity and Collection of Investments Proceeds from Sale, Maturity and Collection of Investments Cost Available-for-sale Debt Securities, Amortized Cost Basis Gross Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Available-for-sale Securities Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities Cash Flow, Supplemental Disclosures [Text Block] Amortizable Intangible Assets Intangible Assets Disclosure [Text Block] Business Combinations Business Combination Disclosure [Text Block] Reconciliation between Basic and Diluted Weighted Average Shares Outstanding Schedule of Weighted Average Number of Shares [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Table Text Block] Property, Plant and Equipment [Table Text Block] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Minimum Maximum [Member] Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Vested​InPeriod​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Vested​InPeriod​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Vested​InPeriod​Awarded​Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​InPeriod​Prior​Year​Awards​Issued​Granted​InCurrent​Year Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​InPeriod​Prior​Year​Awards​Issued​Granted​InCurrent​Year Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Grants​InPeriod​Prior​Year​Awards​Issued​Granted​InCurrent​Year Maximum​Number​OfShares​Available​ToBe​Granted​Under​Award​Stock​Plan Maximum​Number​OfShares​Available​ToBe​Granted​Under​Award​Stock​Plan Maximum​Number​OfShares​Available​ToBe​Granted​Under​Award​Stock​Plan Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod​Weighted​Average​Grant​Date​Fair​Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod​Weighted​Average​Grant​Date​Fair​Value Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​InPeriod​Weighted​Average​Grant​Date​Fair​Value Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​GrantedShares​Awarded​InPeriod Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​GrantedShares​Awarded​InPeriod Share​Based​Compensation​Arrangement​BySharebased​Payment​Award​Equity​Instruments​GrantedShares​Awarded​InPeriod ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Not​Yet​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Not​Yet​Awarded​Shares Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Forfeited​InPeriod​Not​Yet​Awarded​Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSharesNotAwarded ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSharesNotAwarded ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSharesNotAwarded Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Incremental​Increases​InAverage​Stock​Price​From​Initial​Grant​Price Incremental​Increases​InAverage​Stock​Price​From​Initial​Grant​Price Incremental​Increases​InAverage​Stock​Price​From​Initial​Grant​Price Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Attainment​Age​OfStock​Plan Attainment​Age​OfStock​Plan Attainment​Age​OfStock​Plan Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Awarded​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Distributed​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Distributed​Shares​Outstanding​Number Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Distributed​Shares​Outstanding​Number Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Income Tax Contingency [Table] Income Tax Contingency [Table] Tax Law Changes [Axis] Tax Law Changes [Axis] Tax Law Changes [Axis] Tax Law Changes [Domain] Tax Law Changes [Domain] [Domain] for Tax Law Changes [Axis] Tax Cuts and Jobs Act 2017 [Member] Tax Cuts and Jobs Act 2017 [Member] Tax Cuts and Jobs Act 2017 [Member] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Axis] Income Tax Authority, Name [Domain] Income Tax Authority, Name [Domain] Tax Period [Axis] Tax Period [Axis] Tax Period [Domain] Tax Period [Domain] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Other Tax Expense (Benefit) Other Tax Expense (Benefit) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income Tax Expense (Benefit) Income Tax Expense (Benefit) Taxes Payable Taxes Payable Deferred Tax Liabilities, Deferred Expense Deferred Tax Liabilities, Deferred Expense Fair Value Of Assets And Liabilities Statement [Table] Fair Value Of Assets And Liabilities Statement [Table] Fair Value Of Assets And Liabilities Statement [Table] Retail Retail [Member] Retail [Member] National Programs National Programs [Member] National Programs [Member] Wholesale Brokerage Business Combination, Separately Recognized Transactions [Axis] Business Combination, Separately Recognized Transactions [Axis] Business Combination, Separately Recognized Transactions [Domain] Business Combination, Separately Recognized Transactions [Domain] Spain Agency, Inc. (Spain) Spain Agency, Inc. [Member] Spain Agency, Inc. [Member] Bellingham Underwriters, Inc. [Member] Bellingham Underwriters, Inc. [Member] Bellingham Underwriters, Inc. [Member] Fitness Insurance, LLC [Member] Fitness Insurance, LLC [Member] Fitness Insurance, LLC [Member] Other Strategic Benefit Advisors, Inc. [Member] Strategic Benefit Advisors, Inc. [Member] Bentrust Financial, Inc. [Member] Bentrust Financial, Inc. [Member] Bentrust Financial, Inc. [Member] MBA Insurance Agency of Arizona, Inc. [Member] MBA Insurance Agency of Arizona, Inc. [Member] MBA Insurance Agency of Arizona, Inc. [Member] Smith Insurance, Inc. [Member] Smith Insurance, Inc. [Member] Smith Insurance, Inc. [Member] Liberty Insurance Brokers, Inc. and Affiliates [Member] Liberty Insurance Brokers, Inc. and Affiliates [Member] Liberty Insurance Brokers, Inc. and Affiliates [Member] Fair Value Of Assets And Liabilities Statement [Line Items] Fair Value Of Assets And Liabilities Statement [Line Items] Fair Value Of Assets And Liabilities Statement [Line Items] Effective Date of Acquisition Business Acquisition, Effective Date of Acquisition Other Payable Business Acquisition Cost Of Acquired Entity Other Payable Business Acquisition Cost Of Acquired Entity Other Payable Payments to Acquire Businesses, Gross Payments to Acquire Businesses, Gross Recorded Earn-Out Payable Business Acquisitions Contingent Consideration At Fair Value Business Acquisitions Contingent Consideration At Fair Value Business Acquisition Purchase Price Allocation Current Assets Prepaid Expenses And Other Assets Business Acquisitions Purchase Price Allocation Current Assets Cash And Cash Equivalents Business Acquisitions Purchase Price Allocation Current Assets Cash And Cash Equivalents Business Acquisition Purchase Price Allocation Current Assets Prepaid Expenses And Other Assets Business Acquisition Purchase Price Allocation Current Assets Prepaid Expenses And Other Assets Business Acquisition Purchase Price Allocation Current Assets Prepaid Expenses And Other Assets Fixed assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Goodwill Goodwill, Fair Value Disclosure Purchased customer accounts Business Acquisitions Purchase Price Allocation Amortizable Intangible Assets Business Acquisitions Purchase Price Allocation Amortizable Intangible Assets Non-compete agreements Business Acquisitions Purchase Price Allocation Noncompete Agreements Gross Business acquisitions purchase price allocation non-compete agreements gross. Business Acquisitions Purchase Price Allocation Other Noncurrent Assets Business Acquisitions Purchase Price Allocation Other Noncurrent Assets Business Acquisitions Purchase Price Allocation Other Noncurrent Assets Total assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Other current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other Deferred Tax Liabilities, Net Deferred Tax Liabilities, Net Deferred Tax Assets, Net Deferred Tax Assets, Net Other liabilities Business Acquisition Purchase Price Allocation Other Liabilities Assumed Business Acquisition Purchase Price Allocation Other Liabilities Assumed Total liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Net assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Maximum Potential Earn- Out Payable Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Long-Term Debt Instrument Schedule of Long-term Debt Instruments [Table Text Block] Income Statement [Abstract] REVENUES Revenues [Abstract] Commissions and fees Insurance Commissions and Fees Investment income Investment Income, Nonoperating Other income, net Other Income Total revenues EXPENSES Costs and Expenses [Abstract] Employee compensation and benefits Employee Compensation And Benefits The aggregate amount of expenditures for salaries, wages, profit sharing and incentive compensation, and other employee benefits, including pension and other postretirement benefit expense, but excluding share-based compensation.) Non-cash stock-based compensation Other operating expenses Other Cost and Expense, Operating (Gain)/loss on disposal Gain (Loss) on Disposition of Assets Amortization Amortization Depreciation Depreciation Interest Interest Expense Change in estimated acquisition earn-out payables Total expenses Operating Expenses Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income taxes Net income Net Income (Loss) Attributable to Parent Net income per share: Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Dividends declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Non Current Deferred Tax Liabilities [Table Text Block] Schedule of Non Current Deferred Tax Liabilities Summary of Income Tax Contingencies [Table Text Block] Deferred Tax Provision Deferred Tax Provision Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block] Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits [Table Text Block] Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Report Date [Axis] Report Date [Axis] Financial Statement Filing Date [Domain] Financial Statement Filing Date [Domain] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Treasury Stock [Member] Treasury Stock [Member] Retained Earnings [Member] Retained Earnings [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Domain] Adjustments for Change in Accounting Principle [Domain] Adjustments for Error Corrections [Axis] Adjustments for Error Corrections [Axis] Adjustments for Error Correction [Domain] Adjustments for Error Correction [Domain] Common Stock, Shares, Outstanding Common Stock, Shares, Outstanding Stockholders' Equity Attributable to Parent Stockholders' Equity Attributable to Parent Common Stock Issued to Directors Common Stock Issued to Directors Common Stock Issued to Directors Dividends, Cash Dividends, Cash Net Income (Loss) Attributable to Parent Net Unrealized Holding Gain on Available for Sale Securities Net Unrealized Holding Gain on Available for Sale Securities Net Unrealized Holding Gain on Available for Sale Securities Stock Issued During Period, Value, Employee Benefit Plan Stock Issued During Period, Shares, Employee Benefit Plan Stock Issued During Period, Value, Employee Benefit Plan Stock Issued During Period, Value, Employee Benefit Plan Treasury Stock, Value, Acquired, Cost Method Treasury Stock, Value, Acquired, Cost Method Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Common Stock Issued to Directors Shares Common Stock Issued to Directors Shares Common Stock Issued to Directors Shares Stockholders' Equity Attributable to Parent Initial Application Period Cumulative Effect Transition [Abstract] Initial Application Period Cumulative Effect Transition [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Scenario, Forecast [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Deferred Tax Assets Netted Against Deferred Tax Liabilities Deferred Tax Assets Netted Against Deferred Tax Liabilities Deferred Tax Assets Netted Against Deferred Tax Liabilities New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets Reinsurance Disclosures [Abstract] Written Premiums Written, Net [Abstract] Direct premiums Direct Premiums Written Assumed premiums Assumed Premiums Written Ceded premiums Ceded Premiums Written Net premiums Premiums Written, Net Earned Premiums Earned, Net [Abstract] Direct premiums Direct Premiums Earned Assumed premiums Assumed Premiums Earned Ceded premiums Ceded Premiums Earned Net premiums Premiums Earned, Net Text Block [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, Plant and Equipment, Useful Life Property, Plant and Equipment, Useful Life Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Wright National Flood Insurance Company [Member] Quota Share Agreement Quota Share Agreement Member [Member] Quota Share Agreement Member [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Reinsurer Concentration Risk [Member] Reinsurer Concentration Risk [Member] Reinsurance Policy, Type [Axis] Reinsurance Policy, Type [Axis] Reinsurance Policy [Domain] Reinsurance Policy [Domain] Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items] Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items] Ceded rate of premiums under insurance program Percentage of Ceded Premiums Percentage of ceded premiums. Percentage of reinsurance recoverables allowance Percentage of reinsurance recoverables allowance Percentage of reinsurance recoverables allowance. Loss Adjustment Expense Loss Adjustment Expense Loss Adjustment Expense Case Reserves Case Reserves Case Reserves Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount Premiums written net Effective cedes rate under quota share agreement Percentage of flood premiums ceded Percentage of flood premiums ceded. Commission rate, percent of ceded written premiums Reinsurance percentage of ceding commission Reinsurance percentage of ceding commission. Ceded amount Reinsurance Recoverables, Including Reinsurance Premium Paid Reinsurance Recoverables on Unpaid Losses, Gross Reinsurance Recoverables on Unpaid Losses, Gross Prepaid reinsurance premiums Prepaid Reinsurance Premiums Increase (Decrease) in Loss and Loss Adjustment Expense Reserve Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Reserve For Losses And Loss Adjustment Expenses For Reinsurance Liability Reserve For Losses And Loss Adjustment Expenses For Reinsurance Liability Reserve For Losses And Loss Adjustment Expenses For Reinsurance Liability Number of reinsurers Number of reinsurers Number of reinsurers. Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Trading Activity [Axis] Trading Activity [Axis] Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Master Agreement Master Agreement [Member] Master Agreement [Member] New Master Agreement New Master Agreement [Member] New Master Agreement [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Term Loan Term Loan [Member] Term Loan [Member] Revolving Credit Facility Revolving Credit Facility [Member] Uncommitted Facility Uncommitted Facility [Member] Uncommitted Facility [Member] Lender Name [Axis] Lender Name [Axis] Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Auction Market Preferred Securities, Stock Series [Axis] Auction Market Preferred Securities, Stock Series [Axis] Auction Market Preferred Securities, Stock Series, Title [Domain] Auction Market Preferred Securities, Stock Series, Title [Domain] Series C Series C [Member] Series C [Member] Series D Series D [Member] Series D [Member] Series E Series E [Member] Series E [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Senior Notes Due Two Thousand Sixteen [Member] Senior Notes Due Two Thousand Sixteen [Member] Senior Notes Due Two Thousand Sixteen [Member] 5.370% senior notes, Series D, quarterly interest payments, balloon due 2015 Five Point Three Seven Zero Percent Senior Notes Due Two Thousand Fifteen [Member] Five Point Three Seven Zero Percent Senior Notes Due Two Thousand Fifteen [Member] Credit Agreement Credit Agreement [Member] Credit Agreement [Member] Unsecured Senior Notes Unsecured Senior Notes [Member] Unsecured Senior Notes [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Proceeds from Issuance of Debt Proceeds from Issuance of Debt Write off of Deferred Debt Issuance Cost Write off of Deferred Debt Issuance Cost Debt Issuance Costs, Noncurrent, Net Debt Issuance Costs, Noncurrent, Net Unsecured senior notes outstanding Unsecured Debt Debt instrument interest rate stated percentage Debt Instrument, Interest Rate, Stated Percentage Current portion of senior notes Senior Notes, Current Credit facility, outstanding amount Long-term Line of Credit Number of extension periods Debt Instrument, Number of Extension Periods Debt Instrument, Number of Extension Periods Extension period Debt Instrument, Extension Period Debt Instrument, Extension Period Revolving and term loan Debt Instrument Revolving And Term Loan Debt instrument, revolving and term loan Debt instrument, variable interest rate Debt Instrument, Basis Spread on Variable Rate Potential increased in line of credit facility Line of Credit Facility, Maximum Borrowing Capacity Letter of credit fees Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Unsecured revolving credit facility Unsecured Revolving Credit Facility Unsecured Revolving Credit Facility Debt Instrument, Periodic Payment, Principal Debt Instrument, Periodic Payment, Principal Unsecured term loans Unsecured Long-term Debt, Noncurrent Facility fee Line of Credit Facility, Commitment Fee Percentage Proceeds from lines of credit Proceeds from Lines of Credit Debt instrument, face amount Debt Instrument, Face Amount Debt instrument maturity year Debt Instruments Maturity Year Debt Instruments Maturity Year Outstanding debt balance Long-term Debt Notes Payable, Current Notes Payable, Current 30-day Adjusted LIBOR Rate Adjusted Libor Rate Adjusted LIBOR rate Statutory Accounting Practices [Abstract] Statutory Accounting Practices [Abstract] Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Statutory Accounting Practices [Line Items] Statutory Accounting Practices [Line Items] Statutory capital and surplus required Statutory Accounting Practices, Statutory Capital and Surplus Required Statutory capital and surplus Statutory Accounting Practices, Statutory Capital and Surplus, Balance Statutory net Income Statutory Accounting Practices, Statutory Net Income Amount Statutory Financial Information Statutory Financial Information [Text Block] The entire disclosure for statutory financial information. Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Summary of Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Time-Based [Member] Time-Based [Member] Time-Based [Member] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Share​Based​Compensation​Arrangement​ByShare​Based​Payment​Award​Equity​Instruments​Other​Than​Options​Vested​InPeriod​Awarded​Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Percentage​OfPre​Tax​Income Percentage​OfPre​Tax​Income Percentage​OfPre​Tax​Income Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Non-Cash Stock Based Compensation Expense [Abstract] Non-Cash Stock Based Compensation Expense [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Effects of Reinsurance on Premiums Written and Earned Effects of Reinsurance [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Range [Domain] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Asset, Useful Life Finite-Lived Intangible Asset, Useful Life Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Furniture and Fixtures [Member] Furniture and Fixtures [Member] Leasehold Improvements [Member] Leasehold Improvements [Member] Land, Buildings and Improvements [Member] Land, Buildings and Improvements [Member] Property, Plant and Equipment, Gross Property, Plant and Equipment, Gross Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, Plant and Equipment, Net Property, Plant and Equipment, Net Segment Information Segment Reporting Disclosure [Text Block] 5.660% senior notes, Series C, semi-annual interest payments, balloon due 2016 Five Point Six Six Zero Percent Senior Notes Due Two Thousand Sixteen [Member] Five Point Six Six Zero Percent Senior Notes Due Two Thousand Sixteen [Member] 4.500% senior notes, Series E, quarterly interest payments, balloon due 2018 Four Point Five Zero Zero Percent Senior Notes Due Two Thousand Eighteen [Member] Four Point Five Zero Zero Percent Senior Notes Due Two Thousand Eighteen [Member] 4.200% senior notes, semi-annual interest payments, balloon due 2024 Four Point Two Zero Zero Percent Senior Notes Due Two Thousand Twenty Four [Member] Four Point Two Zero Zero Percent Senior Notes Due Two Thousand Twenty Four [Member] 5-year term loan facility, periodic interest and principal payments, LIBOR plus up to 1.750%, expires June 28, 2022 Five Year Term Loan Facility Expires In Two Thousand Twenty-Two [Member] Five Year Term Loan Facility Expires In Two Thousand Twenty-Two [Member] 5-year revolving loan facility, periodic interest payments, currently LIBOR plus up to 1.500%, plus commitment fees up to 0.250%, expires June 28, 2022 Five Year Revolving Loan Facility Expires In Two Thousand Twenty-Two [Member] Five Year Revolving Loan Facility Expires In Two Thousand Twenty-Two [Member] Long-term Debt, Maturities, Repayments of Principal in Year Five Long-term Debt, Maturities, Repayments of Principal in Year Five Current portion of loan facility Line of Credit, Current Total current portion of long-term debt Long-term Debt, Current Maturities Total notes Senior Notes Long-term credit agreements Debt Issuance Costs, Net Debt Issuance Costs, Net Total long-term debt Long-term Debt, Excluding Current Maturities Current portion of long-term debt Total debt Increase (Decrease) in Notes Payable, Current Increase (Decrease) in Notes Payable, Current Asset Acquisitions [Member] Asset Acquisitions [Member] Asset Acquisitions [Member] Book of Business Purchases [Member] Book of Business Purchases [Member] Book of Business Purchases [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other non-current liability Other Noncurrent Liabilities [Member] Services [Member] Various Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Purchased customer accounts Customer Relationships [Member] Non-compete agreements Noncompete Agreements [Member] Extinguishment of Debt [Axis] Extinguishment of Debt [Axis] Extinguishment of Debt, Type [Domain] Extinguishment of Debt, Type [Domain] Accounts payable Accounts Payable [Member] Maximum Future Contingency payments Acquisitions Maximum Future Contingency payments Acquisitions Maximum Future Contingency Payments Acquisitions Number of acquisitions Number of Businesses Acquired Aggregate purchase price of acquisitions Business Acquisitions Purchase Price Allocation Adjustment Purchase Price Business acquisitions purchase price allocation adjustment purchase price. Weighted average life (years) Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Goodwill assigned Goodwill currently deductible for income tax purposes Business Acquisition, Goodwill, Expected Tax Deductible Amount Goodwill currently non-deductible for income tax purposes Business Acquisition Purchase Price Allocation Goodwill Non Deductible Amount The amount of goodwill not deductible for tax purposes. Goodwill related to the recorded earn-out payables Earn Out Payable Not Deductible Until Earned Paid Earn out payable not deductible until earned paid Total revenues related to acquisitions Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Income before income taxes related to acquisitions Business Combination Pro Forma Information Income Loss Before Income Taxes Of Acquiree Since Acquisition Date Actual Business Combination Pro Forma Information Income Loss Before Income Taxes Of Acquiree Since Acquisition Date Actual Estimated acquisition earn-out payables Business Acquisitions Contingent Consideration At Fair Value Net Assets Acquired Payables and Accruals [Abstract] Other Current Liabilities [Table Text Block] Other Accrued Liabilities, Current Accrued expenses and other liabilities Accrued Liabilities, Current Interest Payable, Current Interest Payable, Current Reserve for policy cancellations Reserve for policy cancellations Reserve for policy cancellations Accrued Rent and Vendor Expenses Accrued Rent and Vendor Expenses Accrued Rent and Vendor Expenses Accrued Employee Benefits, Current Accrued Employee Benefits, Current Accrued Bonuses Accrued Bonuses, Current Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Accrued Expenses and Other Liabilities [Table Text Block] [Table Text Block] for Accrued Expenses and Other Liabilities [Table] Schedule of Accrued Liabilities [Table Text Block] Schedule of Accrued Expenses and Other Liabilities [Table Text Block] Schedule of Accrued Expenses and Other Liabilities Deferred Revenue Deferred Revenue Gross Carrying Value Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Carrying Value Intangible Assets, Net (Excluding Goodwill) Weighted Average Life (Years) Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Restricted cash and investments Restricted Cash and Investments, Current Short-term investments Premiums, commissions and fees receivable Premiums Commissions And Fees Receivable Insurance premiums, commissions and fees due from insured or insurance companies that are currently due, including notes receivables, accrued direct bill commissions due from carriers, guaranteed supplemental commissions and profit-sharing contingent commissions, and fees in lieu of commissions earned) Reinsurance recoverable Reinsurance Recoverables, Gross Other current assets Other Assets, Current Total current assets Assets, Current Fixed assets, net Goodwill Goodwill Amortizable intangible assets, net Investments Investments Other assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities and Equity [Abstract] Current Liabilities: Liabilities, Current [Abstract] Premiums payable to insurance companies Premiums Payable To Insurance Companies Insurance premiums payable (net of commissions) to insurance carriers, commissions payable to agents, brokers, third parties, etc that are currently due; also includes other insurance-related liabilities such as surplus lines and other premium related taxes and fees. Losses and loss adjustment reserve Liability for Claims and Claims Adjustment Expense Unearned premiums Unearned Premiums Premium deposits and credits due customers Premium Deposits And Credits Due Customers Liability for net credit balance due customers resulting from changes, cancellation of coverage or payments collected for premiums not yet effective. Accounts payable Accounts Payable, Current Current portion of long-term debt Total current liabilities Liabilities, Current Long-term debt less unamortized discount and debt issuance costs Deferred income taxes, net Deferred Tax Liabilities, Net, Noncurrent Other liabilities Other Liabilities, Noncurrent Shareholders’ Equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, par value $0.10 per share; authorized 280,000 shares; issued 148,824 shares and outstanding 138,105 shares at 2017, issued 148,107 shares and outstanding 140,104 shares at 2016 Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Treasury stock, at cost 10,719 and 8,003 shares at 2017 and 2016, respectively Treasury Stock, Value Retained earnings Retained Earnings (Accumulated Deficit) Total shareholders’ equity Total liabilities and shareholders’ equity Liabilities and Equity Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table] Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table] Two Thousand Seventeen Acquisition [Member] [Domain] Two Thousand Seventeen Acquisition [Member] [Domain] Two Thousand Seventeen Acquisition [Member] [Domain] Two Thousand Fifteen Acquisitions [Member] Two Thousand Fifteen Acquisitions [Member] Two Thousand Fifteen Acquisitions [Member] Nonrecurring Adjustment [Axis] Nonrecurring Adjustment [Axis] Nonrecurring Adjustment [Domain] Nonrecurring Adjustment [Domain] Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items] Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items] Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Business Combination Pro Forma Information Income Loss Before Income Taxes Of Acquiree Since Acquisition Date Actual Total revenues Business Acquisition, Pro Forma Revenue Income before income taxes Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax Net income Business Acquisition, Pro Forma Net Income (Loss) Basic (in dollars per share) Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Diluted Weighted Average Basic Shares Outstanding, Pro Forma Weighted Average Basic Shares Outstanding, Pro Forma Weighted average number of shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Pro Forma Weighted Average Shares Outstanding, Diluted Pro Forma Weighted Average Shares Outstanding, Diluted Operating Leases, Rent Expense Operating Leases, Rent Expense Operating Leases, Future Minimum Payments Due, Next Twelve Months Operating Leases, Future Minimum Payments Due, Next Twelve Months Operating Leases, Future Minimum Payments, Due in Two Years Operating Leases, Future Minimum Payments, Due in Two Years Operating Leases, Future Minimum Payments, Due in Three Years Operating Leases, Future Minimum Payments, Due in Three Years Operating Leases, Future Minimum Payments, Due in Four Years Operating Leases, Future Minimum Payments, Due in Four Years Operating Leases, Future Minimum Payments, Due in Five Years Operating Leases, Future Minimum Payments, Due in Five Years Operating Leases, Future Minimum Payments, Due Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Operating Leases, Future Minimum Payments Due Operating Leases, Future Minimum Payments Due Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Four Long-term Debt, Maturities, Repayments of Principal in Year Four Long-term Debt, Maturities, Repayments of Principal after Year Five Long-term Debt, Maturities, Repayments of Principal after Year Five Long-term Debt, Fair Value Long-term Debt, Fair Value Property, Plant and Equipment Disclosure [Text Block] Property, Plant and Equipment Disclosure [Text Block] Operating Loss Carryforwards State Operating Loss Carryforwards State Operating Loss Carryforwards State Operating Loss Carryforwards Operating Loss Carryforwards Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Deferred Tax Assets, Valuation Allowance Deferred Tax Assets, Valuation Allowance Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Deferred Tax Assets, Operating Loss Carryforwards Deferred Tax Assets, Operating Loss Carryforwards Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Liability for Uncertain Tax Positions, Current Liability for Uncertainty in Income Taxes, Current Income Taxes Paid Unrecognized Tax Benefits Unrecognized Tax Benefits Deferred Tax Liabilities, Property, Plant and Equipment Deferred Tax Liabilities, Property, Plant and Equipment deferred profit sharing contingent commissions deferred profit sharing contingent commissions deferred profit sharing contingent commissions Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Current Federal Tax Expense (Benefit) Current Federal Tax Expense (Benefit) Current State and Local Tax Expense (Benefit) Current State and Local Tax Expense (Benefit) Current Foreign Tax Expense (Benefit) Current Foreign Tax Expense (Benefit) Deferred Federal Income Tax Expense (Benefit) Deferred Federal Income Tax Expense (Benefit) Current Income Tax Expense (Benefit) Current Income Tax Expense (Benefit) Deferred State and Local Income Tax Expense (Benefit) Deferred State and Local Income Tax Expense (Benefit) Deferred Foreign Income Tax Expense (Benefit) Deferred Foreign Income Tax Expense (Benefit) Deferred Foreign Income Tax Expense (Benefit) Deferred Tax Liability Not Recognized, Determination of Deferred Tax Liability is Not Practicable, Undistributed Earnings of Foreign Subsidiaries Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment, Percent Tax Reform Act Deferred Tax Revaluation and Transition Tax Impact Tax Reform Act Deferred Tax Revaluation and Transition Tax Impact Tax Reform Act Deferred Tax Revaluation and Transition Tax Impact Deferred Tax Liabilities, Deferred Expense Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Effective Income Tax Rate Reconciliation, Percent Effective Income Tax Rate Reconciliation, Percent Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Deferred Tax Liabilities, Goodwill and Intangible Assets Deferred Tax Liabilities, Goodwill and Intangible Assets Non Current Deferred Tax Liability Non Current Deferred Tax Liability Non Current Deferred Tax Liability Deferred Tax Assets, Net, Noncurrent Deferred Tax Assets, Net, Noncurrent Amortization expense estimated, year one (2015) Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Amortization expense estimated, year two (2016) Finite-Lived Intangible Assets, Amortization Expense, Year Two Amortization expense estimated, year three (2017) Finite-Lived Intangible Assets, Amortization Expense, Year Three Amortization expense estimated, year four (2018) Finite-Lived Intangible Assets, Amortization Expense, Year Four Amortization expense estimated, year five (2019) Finite-Lived Intangible Assets, Amortization Expense, Year Five U.S. Treasury securities, obligations of U.S. Government agencies and Municipals US Treasury Securities [Member] Corporate debt Corporate Debt Securities [Member] Available-for-sale Debt Securities, Amortized Cost Basis Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Fair Value, Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Unrealized Losses, Less than 12 Months Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses Accumulated In AOCI Amount of accumulated pre-tax unrealized loss on investments in available-for-sale securities that have been in a loss position for less than twelve months recognized in Accumulated Other Comprehensive Income (AOCI). Fair Value, 12 Months or More Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Unrealized Losses, 12 Months or More Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In AOCI Amount of accumulated pre-tax unrealized loss on securities classified as available-for-sale that have been in a loss position for twelve months or longer recognized in Accumulated Other Comprehensive Income (AOCI). Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses Accumulated In AOCI Amount of accumulated pre-tax unrealized loss on securities classified as available-for-sale recognized in Accumulated Other Comprehensive Income (AOCI). Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Available-for-sale Securities Statement of Cash Flows [Abstract] Cash, Cash Equivalents and Restricted Cash Cash, Cash Equivalents and Restricted Cash Cash, Cash Equivalents and Restricted Cash Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Deferred income taxes Deferred Income Tax Expense (Benefit) Amortization of debt discount Amortization of Debt Discount (Premium) Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Amortization Expense Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Amortization Expense Accretion (Amortization) of Discounts and Premiums, Investments Accretion (Amortization) of Discounts and Premiums, Investments Income tax benefit from exercise of shares from the stock benefit plans Excess Tax Benefit from Share-based Compensation, Operating Activities Payments On Acquisition Earn Outs In Excess Of Original Estimated Payables Payments On Acquisition Earn Outs In Excess Of Original Estimated Payables Payments on acquisition earn-outs in excess of original estimated payables. Loss/(gain) on sales of investments, fixed assets and customer accounts Net Loss Gain On Sales Of Investments Fixed Assets And Customer Accounts Net loss (gain) on sales of investments, fixed assets and customer accounts Changes in operating assets and liabilities, net of effect from acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Premiums, commissions and fees receivable (increase) Increase Decrease In Premiums Commission And Fees Receivable The net change during the reporting period in other amounts due to the reporting entity, which are not otherwise defined in the taxonomy. Reinsurance recoverables (increase) Increase (Decrease) in Reinsurance Recoverable Prepaid reinsurance premiums (increase) decrease Increase (Decrease) in Prepaid Reinsurance Premiums Other assets (increase) Increase (Decrease) in Other Operating Assets Premiums payable to insurance companies decrease Increase Decrease In Premiums Payable To Insurance Companies The net change during the reporting period in the premiums payable to insurance companies. Premium deposits and credits due customers increase (decrease) Increase Decrease In Premium Deposits And Credits Due Customers Decrease Increase The net change during the reporting period in the premiums deposits and credits due customers. Losses and loss adjustment reserve increase Increase Decrease For Loss And Loss Adjustment Expense Increase decrease for loss and loss adjustment expense. Unearned premiums increase (decrease) Increase (Decrease) in Unearned Premiums Accounts payable increase Increase (Decrease) in Accounts Payable Accrued expenses and other liabilities increase Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Other liabilities (decrease) Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Additions to fixed assets Payments to Acquire Property, Plant, and Equipment Payments for businesses acquired, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Proceeds from sales of fixed assets and customer accounts Proceeds from Sale of Productive Assets Purchases of investments Payments to Acquire Investments Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Payments on acquisition earn-outs Payments On Acquisition Earn Outs Payments on acquisition earn-outs Payments on long-term debt Repayments of Long-term Debt Income tax benefit from exercise of shares from the stock benefit plans Excess Tax Benefit from Share-based Compensation, Financing Activities Issuances of common stock for employee stock benefit plans Proceeds from Stock Options Exercised Repurchase of stock benefit plan shares for employees to fund tax withholdings Repurchase Of Stock Benefit Plan Shares For Employees To Fund Tax Withholdings Repurchase of stock benefit plan shares for employees to fund tax withholdings Purchase of treasury stock Payments for Repurchase of Common Stock Settlement (prepayment) of accelerated share repurchase program Payments for Repurchase of Other Equity Cash dividends paid Payments of Dividends Net cash used in by financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations Payments of Debt Issuance Costs Payments of Debt Issuance Costs Net increase (decrease) in cash and cash equivalents inclusive of restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Proceeds from Lines of Credit Amortized Cost Available-for-sale Securities, Amortized Cost Basis [Abstract] Due in one year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis Due after one year through five years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis Due after five years through ten years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis Amortized Cost, Total Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis Fair Value Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract] Due in one year or less Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Due after one year through five years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Due after five years through ten years Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value Fair Value, Total Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value Accelerated Share Repurchases [Table] Accelerated Share Repurchases [Table] Accelerated Share Repurchases, Date [Axis] Accelerated Share Repurchases, Date [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Third Accelerated Share Repurchase Program [Member] Third Accelerated Share Repurchase Program [Member] Third Accelerated Share Repurchase Program [Member] Third Accelerated Share Repurchase Agreement [Member] Accelerated Share Repurchase Agreement [Member] Accelerated Share Repurchase Agreement [Member] Second Accelerated Share Repurchase Agreement [Member] Second Accelerated Share Repurchase Agreement [Member] Second Accelerated Share Repurchase Agreement [Member] Third Accelerated Share Repurchase Agreement [Member] Third Accelerated Share Repurchase Agreement [Member] Third Accelerated Share Repurchase Agreement [Member] Share Repurchase Executed Part 1 [Member] Share Repurchase Executed Part 1 [Member] Share Repurchase Executed Part 1 [Member] Share Repurchase Executed Part 2 [Member] Share Repurchase Executed Part 2 [Member] Share Repurchase Executed Part 2 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Accelerated Share Repurchases [Line Items] Accelerated Share Repurchases [Line Items] Treasury Stock, Shares Treasury Stock, Shares Stock Repurchase Program, Authorized Amount Stock Repurchase Program, Authorized Amount Treasury Stock, Value Stock Repurchase Program, Remaining Authorized Repurchase Amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Treasury Stock, Shares, Acquired Treasury Stock, Shares, Acquired Treasury Stock, Value, Acquired, Cost Method Proceeds from Sale of Short-term Investments Proceeds from Sale of Short-term Investments Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Beginning balance Goodwill of acquired businesses Goodwill, Acquired During Period Goodwill disposed of relating to sales of businesses Goodwill, Written off Related to Sale of Business Unit Ending balance Legal and Regulatory Proceedings Commitments and Contingencies Disclosure [Text Block] Two Thousand Sixteen Acquisition [Member] Two Thousand Sixteen Acquisition [Member] Two Thousand Sixteen Acquisition [Member] Business Acquisition, Pro Forma Revenue Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax Business Acquisition, Pro Forma Net Income (Loss) Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Basic Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted Schedule of Investments in Fixed Maturity Securities Available For Sale Securities Debt Maturities Table [Table Text Block] Available For Sale Securities Debt Maturities Table [Text Block] Summary of Unrealized Loss Position Unrealized Loss Position Investments Table [Table Text Block] Unrealized Loss Position Investments Table [Text Block] Amortized Cost and Fair Value of Fixed Maturity Securities by Contractual Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Losses and Loss Adjustment Reserve Reinsurance Loss, Loss Adjustment Expenses [Text Block] Reinsurance Loss, Loss Adjustment Expenses [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Line of credit facility, expiration period Line of Credit Facility, Expiration Period Debt instrument, interest rate, stated percentage Line of credit facility, commitment fee percentage Line of credit facility, expiration date Line of Credit Facility, Expiration Date Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Quarterly Financial Information [Text Block] Quarterly Financial Information [Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Average Annual Operating Profit Earned Period Maximum Average Annual Operating Profit Earned Period Maximum Average Annual Operating Profit Earned Period Maximum (years) Fair Value of Financial Instruments, Policy [Policy Text Block] Fair Value of Financial Instruments, Policy [Policy Text Block] Nature of Operations Significant Accounting Policies [Text Block] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Consolidation, Policy [Policy Text Block] Consolidation, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Restricted Cash and Investments Premiums Commissions and Fees Receivable Policy [Text Block] Restricted Cash and Investments Premiums Commissions and Fees Receivable Policy [Text Block] Restricted Cash and Investments Premiums Commissions and Fees Receivable Policy [Text Block] Investment, Policy [Policy Text Block] Investment, Policy [Policy Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Reinsurance Accounting Policy [Policy Text Block] Reinsurance Accounting Policy [Policy Text Block] Unpaid Policy Claims and Claims Adjustment Expense, Policy [Policy Text Block] Unpaid Policy Claims and Claims Adjustment Expense, Policy [Policy Text Block] Insurance Premiums Revenue Recognition, Policy [Policy Text Block] Insurance Premiums Revenue Recognition, Policy [Policy Text Block] Net income attributable to unvested awarded performance stock Net Income Attributable To Unvested Awarded Performance Stock Net income attributable to unvested awarded performance stock Net income attributable to common shares Net Income (Loss) Available to Common Stockholders, Basic Weighted average number of common shares outstanding - basic (in shares) Weighted Average Number of Shares Issued, Basic Less unvested awarded performance stock included in weighted average number of common shares outstanding - basic (in shares) Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights Weighted average number of common shares outstanding for basic earnings per common share (in shares) Weighted Average Number of Shares Outstanding, Basic Dilutive effect of stock options (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average number of shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Subsegments Consolidation Items [Axis] Subsegments Consolidation Items [Axis] Subsegments Consolidation Items [Domain] Subsegments Consolidation Items [Domain] Segment Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Employee Savings Plan [Abstract] Employee Savings Plan [Abstract] Compensation and Employee Benefit Plans [Text Block] Compensation and Employee Benefit Plans [Text Block] Service Period Eligible to Participate for Employee Savings Plan Service Period Eligible to Participate for Employee Savings Plan Service Period Eligible to Participate for Employee Savings Plan Defined Contribution Plan, Employer Matching Contribution, Percent of Match Defined Contribution Plan, Employer Matching Contribution, Percent of Match Discretionary Profit Sharing Contribution Percentage of Employees Salary Discretionary Profit Sharing Contribution Percentage of Employees Salary Discretionary Profit Sharing Contribution Percentage of Employees Salary Defined Benefit Plan, Contributions by Employer Defined Benefit Plan, Contributions by Employer Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Treasury stock shares (in shares) Tax effect of accumulated other comprehensive income Other Comprehensive Income (Loss), Tax Operating Segments Operating Segments [Member] Other Segment Reconciling Items [Member] Interest expense Income before income taxes Total assets Capital expenditures Amortizable Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Accelerated Share Repurchases, Date [Domain] Accelerated Share Repurchases, Date [Domain] Accelerated Share Repurchase Agreement [Member] Treasury Stock Acquired, Average Cost Per Share Treasury Stock Acquired, Average Cost Per Share Fair value of common stock repurchased Operating Expenses Earnings Per Share, Basic Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-Lived Intangible Assets [Table] Indefinite-lived Intangible Assets [Line Items] Indefinite-lived Intangible Assets [Line Items] Nature of Operations Nature Of Operation Policy [Text Block] Nature Of Operation Policy. Business Combination, Separately Recognized Transactions [Table] Business Combination, Separately Recognized Transactions [Table] National Programs Divisions [Member] National Programs Divisions [Member] National Programs Divisions [Member] Business Combination, Separately Recognized Transactions [Line Items] Business Combination, Separately Recognized Transactions [Line Items] Cash Paid Subsidiary Dividend Restrictions Dividend Payment Restrictions [Text Block]