Earnings Per Share [Abstract] Net income Net Income (Loss) Attributable to Parent 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 Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Statement of Cash Flows [Abstract] Schedule of Cash and Cash Equivalents [Table] Schedule of 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 [Line Items] Cash and Cash Equivalents [Line Items] Document Period End Date Document Period End Date 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] Amortization Amortization Depreciation Depreciation Non-cash stock-based compensation Share-based Compensation Change in estimated acquisition earn-out payables Change In Estimated Acquisition Earn Out Payable Change In Estimated Acquisition Earn Out Payable 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. Net 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 decrease (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 decrease (increase) Increase (Decrease) in Reinsurance Recoverable Prepaid reinsurance premiums 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 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 (decrease) increase Increase Decrease For Loss And Loss Adjustment Expense Increase decrease for loss and loss adjustment expense. Unearned premiums (decrease) Increase (Decrease) in Unearned Premiums Accounts payable increase Increase (Decrease) in Accounts Payable Accrued expenses and other liabilities (decrease) 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 Proceeds from Sale, Maturity and Collection of Investments Proceeds from Sale, Maturity and Collection of 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 of accelerated share repurchase program Payments for Repurchase of Other Equity Cash dividends paid Payments of Dividends Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations Payments of Debt Issuance Costs Payments of Debt Issuance Costs Net increase in cash and cash equivalents inclusive of restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents inclusive of restricted cash at end of period Cash and Cash Equivalents, at Carrying Value Condensed Financial Information of Parent Company Only Disclosure [Abstract] Basis of Financial Reporting Condensed Financial Information of Parent Company Only Disclosure [Text Block] Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Other Segment Reconciling Items [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Services Retail [Member] Retail [Member] National Programs National Programs [Member] National Programs [Member] Wholesale Brokerage Wholesale Brokerage [Member] Wholesale Brokerage [Member] Services Services [Member] Services [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Total revenues Revenues Investment income Investment Income, Nonoperating Interest expense Interest Expense Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Total assets Assets Capital expenditures Investments, Debt and Equity Securities [Abstract] 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 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 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 Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract] Subsidiary Dividend Restrictions Dividend Payment Restrictions [Text Block] Reinsurance Disclosures [Abstract] Effects of Reinsurance on Premiums Written and Earned Effects of Reinsurance [Table Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Goodwill, Written off Related to Sale of Business Unit Goodwill, Written off Related to Sale of Business Unit Beginning balance Goodwill Goodwill of acquired businesses Goodwill, Acquired During Period Ending balance Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Combinations - Asset Deals [Member] Business Combinations - Asset Deals [Member] Business Combinations - Asset Deals [Member] Other Acquisitions [Member] Other Acquisitions [Member] Other Acquisitions [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] 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] Business Acquisition [Line Items] Business Acquisition [Line Items] Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets 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. Payments to Acquire Businesses, Gross Payments to Acquire Businesses, Gross Weighted average life (years) Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Goodwill assigned Goodwill, Fair Value Disclosure Goodwill currently deductible for income tax purposes Business Acquisition, Goodwill, Expected Tax Deductible Amount 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 Acquisition Earn Out Payables Business acquisition earn out payables. Maximum Future Contingency payments Acquisitions Maximum Future Contingency payments Acquisitions Maximum Future Contingency Payments Acquisitions Segment Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Text Block [Abstract] Operating Leases, Future Minimum Payments Due Operating Leases, Future Minimum Payments Due Share-based Compensation Beginning balance 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 Ending balance Cash and Cash Equivalents [Abstract] Statement [Table] Statement [Table] 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] Statement [Line Items] Statement [Line Items] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted Cash and Cash Equivalents Restricted Cash and Cash Equivalents Fair Value Of Assets And Liabilities Statement [Table] Fair Value Of Assets And Liabilities Statement [Table] Fair Value Of Assets And Liabilities Statement [Table] Business Combination, Separately Recognized Transactions [Axis] Business Combination, Separately Recognized Transactions [Axis] Business Combination, Separately Recognized Transactions [Domain] Business Combination, Separately Recognized Transactions [Domain] 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] Recorded Earn-Out Payable Business Acquisitions Contingent Consideration At Fair Value Business Acquisitions Contingent Consideration At Fair Value Other current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Fixed assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Goodwill 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. Total assets acquired Other current liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other Deferred Tax Liabilities, Net Deferred Tax Liabilities, Net 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 Statutory Accounting Practices [Abstract] Statutory Accounting Practices [Abstract] Statutory Financial Information Statutory Financial Information [Text Block] The entire disclosure for statutory financial information. Debt Disclosure [Abstract] Long-Term Debt Debt Disclosure [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] 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 E [Member] Series E [Member] Series E [Member] Trading Activity [Axis] Trading Activity [Axis] Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Master Agreement [Member] Master Agreement [Member] Master Agreement [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Lender Name [Axis] Lender Name [Axis] Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 5.660% senior notes, Series C, semi-annual interest payments, balloon due 2016 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] 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] Unsecured Senior Notes [Member] Unsecured Senior Notes [Member] Unsecured Senior Notes [Member] 4.200% senior notes, semi-annual interest payments, net of the unamortized discount, 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] Term Loan [Member] Term Loan [Member] Term Loan [Member] Five Year Term Loan Facility Expires In Two Thousand Ninteen Current [Member] Five Year Term Loan Facility Expires In Two Thousand Ninteen Current [Member] Five Year Term Loan Facility Expires In Two Thousand Ninteen Current [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] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Line of credit facility, expiration period Line of Credit Facility, Expiration Period Line of Credit Facility, Commitment Fee Percentage Line of Credit Facility, Commitment Fee Percentage Debt instrument, interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Debt instrument maturity year Debt Instruments Maturity Year Debt Instruments Maturity Year Debt instrument, variable interest rate Debt Instrument, Basis Spread on Variable Rate Line of credit facility, expiration date Line of Credit Facility, Expiration Date Statement of Financial Position [Abstract] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] ASSETS Assets [Abstract] Current Assets: Assets, Current [Abstract] Restricted cash and investments Restricted Cash and Investments, Current Short-term investments 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 Prepaid reinsurance premiums Prepaid Reinsurance Premiums Other current assets Other Assets, Current Total current assets Assets, Current Fixed assets, net Property, Plant and Equipment, Net Goodwill Amortizable intangible assets, net Intangible Assets, Net (Excluding Goodwill) Investments Investments Other assets Other Assets, Noncurrent Total 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 Accrued expenses and other liabilities Accrued Liabilities, Current Current portion of long-term debt Long-term Debt, Current Maturities Total current liabilities Liabilities, Current Long-term debt less unamortized discount and debt issuance costs Long-term Debt, Excluding Current Maturities 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 148,838 shares and outstanding 139,518 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 at 9,319 shares at 2017 and 8,003 shares at 2016, respectively Treasury Stock, Value Retained earnings Retained Earnings (Accumulated Deficit) Total shareholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and shareholders’ equity Liabilities and Equity Supplemental Cash Flow Elements [Abstract] Summary of Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Statutory Accounting Practices [Table] Statutory Accounting Practices [Table] Subsegments [Axis] Subsegments [Axis] Subsegments [Domain] Subsegments [Domain] Wright Flood Wright National Flood Insurance Company [Member] Wright National Flood Insurance Company [Member] 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 Goodwill Goodwill and Intangible Assets Disclosure [Text Block] 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] U.S. Treasury securities, obligations of U.S. Government agencies and Municipalities US Treasury Securities [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Available-for-sale Securities Available-for-sale Securities 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 Proceeds from Sale of Other Investments Proceeds from Sale of Other Investments Investment security maturity date, start Investment Maturity Date Range Start Investment security maturity date, End Investment Maturity Date Range End Gross realized gains and losses of securities Available-for-sale Securities, Restrictions, Additional Information Investments on deposit with the state insurance department Assets Held by Insurance Regulators Net Income Per Share Earnings Per Share [Text Block] Schedule of Restricted Cash and Cash Equivalents [Table] Schedule of Restricted Cash and Cash Equivalents [Table] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents Items [Line Items] 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 payable 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 Business Acquisition Cost of Entity Note Payable Notes Issued Scenario, Forecast [Member] Scenario, Forecast [Member] Minimum Minimum [Member] Master Agreement New Master Agreement New Master Agreement [Member] New Master Agreement [Member] Credit Facility [Domain] Term Loan Revolving Credit Facility [Member] Uncommitted Facility Uncommitted Facility [Member] Uncommitted Facility [Member] Series C Series C [Member] Series C [Member] Series D Series D [Member] Series D [Member] Series E Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Credit Agreement Credit Agreement [Member] Credit Agreement [Member] Unsecured Senior Notes Unsecured senior notes outstanding Unsecured Debt 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 Potential increased in line of credit facility Line of Credit Facility, Maximum Borrowing Capacity Unsecured revolving credit facility Unsecured Revolving Credit Facility Unsecured Revolving Credit Facility Write off of Deferred Debt Issuance Cost Write off of Deferred Debt Issuance Cost Debt Issuance Costs, Noncurrent, Net Debt Issuance Costs, Noncurrent, Net Debt Instrument, Periodic Payment, Principal Debt Instrument, Periodic Payment, Principal Proceeds from Issuance of Debt Proceeds from Issuance of Debt Unsecured term loans Unsecured Long-term Debt, Noncurrent Facility fee Debt instrument, face amount Debt Instrument, Face Amount Outstanding debt balance Long-term Debt Notes Payable, Current Notes Payable, Current 30-day Adjusted LIBOR Rate Adjusted Libor Rate Adjusted LIBOR rate Equity [Abstract] Shareholders' Equity Stockholders' Equity Note Disclosure [Text Block] Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities Cash Flow, Supplemental Disclosures [Text Block] Business Combinations Business Combination Disclosure [Text Block] 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 Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock shares (in shares) Treasury Stock, Shares Long-Term Debt Instrument Schedule of Long-term Debt Instruments [Table Text Block] Amortizable Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Dividend Restrictions [Table] Dividend Restrictions [Table] Dividend Restrictions [Table] 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 Ordinary dividends payment description Statutory Dividend Payment Restrictions Disclosure Maximum dividend payout that may be made without prior approval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Document And Entity Information [Abstract] Document and Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag 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 Corporate debt Corporate Debt Securities [Member] Available-for-sale Securities, Debt Maturities, Single Maturity Date Available-for-sale Securities, Debt Maturities, Single Maturity Date 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 Changes in Carrying Value of Goodwill by Operating Segment Schedule of Goodwill [Table Text Block] Subsegments Consolidation Items [Axis] Subsegments Consolidation Items [Axis] Subsegments Consolidation Items [Domain] Subsegments Consolidation Items [Domain] Losses and Loss Adjustment Reserve Reinsurance Loss, Loss Adjustment Expenses [Text Block] Reinsurance Loss, Loss Adjustment Expenses [Text Block] Amortizable Intangible Assets Intangible Assets Disclosure [Text Block] Current portion of loan facility Line of Credit, Current Total current portion of long-term debt Total notes Senior Notes Long-term credit agreements Debt Issuance Costs, Gross Debt Issuance Costs, Gross Total long-term debt Current portion of long-term debt Total debt 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 Reconciliation between Basic and Diluted Weighted Average Shares Outstanding Schedule of Weighted Average Number of Shares [Table Text Block] Accelerated Share Repurchases [Table] Accelerated Share Repurchases [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Repurchase Agreements [Member] Repurchase Agreements [Member] Accelerated Share Repurchases [Line Items] Accelerated Share Repurchases [Line Items] Shares repurchased, authorized amount Stock Repurchase Program, Authorized Amount Shares repurchased, number of shares received initially (in shares) Fair value of common stock repurchased Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Gross Carrying Value Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Carrying Value Weighted Average Life (Years) Finite-Lived Intangible Asset, Useful Life 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. Number of reportable segments Number of Reportable Segments Organization, Consolidation and Presentation of Financial Statements [Abstract] Nature of Operations Nature Of Operation Policy [Text Block] Nature Of Operation Policy. Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table] Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table] 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) Net income per share: Basic (in dollars per share) Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic Diluted (in dollars per share) 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 Nature of Operations Nature of Operations [Text Block] Schedule of Held-to-maturity Securities [Table] Schedule of Held-to-maturity Securities [Table] Debt Security [Axis] Debt Security [Axis] Major Types of Debt Securities [Domain] Major Types of Debt Securities [Domain] Schedule of Held-to-maturity Securities [Line Items] Schedule of Held-to-maturity Securities [Line Items] 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] Business Combination, Separately Recognized Transactions [Table] Business Combination, Separately Recognized Transactions [Table] Various Various [Member] Various [member] Business Combination, Separately Recognized Transactions [Line Items] Business Combination, Separately Recognized Transactions [Line Items] Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Cash Paid Other Payable Business Acquisition Cost Of Acquired Entity Other Payable Business Acquisition Cost Of Acquired Entity Other Payable Net Assets Acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other Deferred Tax Liabilities, Net 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). Income Statement [Abstract] REVENUES Revenues [Abstract] Commissions and fees Insurance Commissions and Fees 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.) Other operating expenses Other Cost and Expense, Operating Loss/(gain) on disposal Gain (Loss) on Disposition of Assets Interest Total expenses Operating Expenses Income before income taxes Income taxes Income Tax Expense (Benefit) Dividends declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Quota Share Agreement Quota Share Agreement Member [Member] Quota Share Agreement Member [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. Expenses and allowance rate received in premiums Percentage of reinsurance recoverables allowance Percentage of reinsurance recoverables allowance. Premiums written net Ceded Premiums Written 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 Ceded unpaid loss Reinsurance Recoverable for Unpaid Claims and Claims Adjustments 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 expense 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. 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] Additions, payments, and net changes, as well as interest expense accretion on estimated acquisition earn-out payables Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Legal and Regulatory Proceedings Commitments and Contingencies Disclosure [Text Block] Written Premiums Written, Net [Abstract] Direct premiums Direct Premiums Written Ceded premiums Net premiums Premiums Written, Net Earned Premiums Earned, Net [Abstract] Direct premiums Direct Premiums Earned Ceded premiums Ceded Premiums Earned Net premiums Premiums Earned, Net