Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2013 Plan 2013 Plan [Member] 2013 Plan [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Shares reserved for future issuance (shares) Common Stock, Capital Shares Reserved for Future Issuance Quarterly Financial Information Disclosure [Abstract] Schedule of quarterly financial information Quarterly Financial Information [Table Text Block] Condensed Financial Information of Parent Company Only Disclosure [Abstract] Condensed Financial Statements [Table] Condensed Financial Statements [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Parent Parent Company [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Investment in subsidiaries Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Fixed maturities Available-for-sale Securities, Debt Securities Equity securities – at fair value (cost $2,372 and $1,908) Available-for-sale Securities, Equity Securities Short-term investments - at fair value (amortized cost $506 and $509) Short-term Investments Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Other assets Other Assets Total assets Assets Long-term debt Long-term Debt Other liabilities Other Liabilities Payable to affiliates Due to Affiliate Shareholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and shareholders’ equity Liabilities and Equity Statement of Cash Flows [Abstract] Operating Activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net earnings Net Income (Loss) Attributable to Parent Adjustments: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation Depreciation Amortization Accretion (Amortization) of Discounts and Premiums, Investments Net realized gains on investments Realized Investment Gains (Losses) Loss on disposal of property and equipment Assets Disposed of by Method Other than Sale, in Period of Disposition, Gain (Loss) on Disposition Share-based compensation expense Share-based Compensation Excess tax benefits from share-based payment arrangements Excess Tax Benefit from Share-based Compensation, Operating Activities Activity related to rabbi trust Non-Cash Activity Related to Rabbi Trust Non-cash activity related to rabbi trust Change in accrued investment income Increase (Decrease) in Accrued Investment Income Receivable Change in agents’ balances and premium receivable Increase (Decrease) in Premiums Receivable Change in reinsurance receivables Increase (Decrease) in Reinsurance Recoverable Change in deferred policy acquisition costs Increase (Decrease) in Deferred Policy Acquisition Costs Change in other assets Increase (Decrease) in Other Operating Assets Change in unpaid losses and loss adjustment expenses Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve Change in unearned premium Increase (Decrease) in Unearned Premiums Change in other liabilities Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities: Payments to Acquire Investments [Abstract] Purchases of fixed maturities Payments to Acquire Available-for-sale Securities, Debt Purchases of equity securities Payments to Acquire Available-for-sale Securities, Equity Purchases of short-term investments Payments to Acquire Short-term Investments Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Maturities and redemptions of fixed maturities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Maturities and redemptions of short-term investments Proceeds from Maturities, Prepayments and Calls of Short-term Investments Proceeds from sale of fixed maturities Proceeds from Sale of Available-for-sale Securities, Debt Proceeds from sale of equity securities Proceeds from Sale of Available-for-sale Securities, Equity Proceeds from sale of short-term investments Proceeds from Sale of Short-term Investments Proceeds from sale of property and equipment Proceeds from Sale of Property, Plant, and Equipment Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from stock options exercised and employee stock purchases Proceeds from Stock Options Exercised Excess tax benefits from share-based payment arrangements Excess Tax Benefit from Share-based Compensation, Financing Activities Principal payments under capital lease obligations Repayments of Long-term Capital Lease Obligations Acquisition of treasury stock Payments for Repurchase of Common Stock Dividends paid to shareholders Payments of Ordinary Dividends, Common Stock Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Additional Information [Abstract] Additional Financial Information Disclosure [Abstract] Allowance for Doubtful Accounts Receivable [Roll Forward] Allowance for Doubtful Accounts Receivable [Roll Forward] Beginning balance Allowance for Doubtful Accounts Receivable Provision for losses Provision for Doubtful Accounts Uncollectible amounts written off Allowance for Doubtful Accounts Receivable, Write-offs Ending balance Supplemental Cash Flow Elements [Abstract] Negative cash book balances Outstanding Checks Outstanding Checks Debt Disclosure [Abstract] Schedule of long-term debt Schedule of Long-term Debt Instruments [Table Text Block] Accounting Policies [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Real Estate Related [Member] Land, Buildings and Improvements [Member] Computer Equipment & Software [Member] Computer Equipment and Software [Member] Computer Equipment and Software [Member] Furniture & Fixtures [Member] Furniture and Fixtures [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Gross Asset Property, Plant and Equipment, Gross Accumulated Depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Net Asset Property, Plant and Equipment, Net Capital Leases [Abstract] Leases, Capital [Abstract] Capital leases net of depreciation Capital Leases, Balance Sheet, Assets by Major Class, Net Capital lease accumulated depreciation Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation Segment Reporting [Abstract] Number of operating segments Number of Operating Segments Number of vehicles in fleet in target businesses (or fewer) Number of Vehicles in Fleet in Target Customers Number of Vehicles in Fleet in Target Customers Average vehicles per policy Average Number of Vehicles Per Insurance Policy Average Number of Vehicles Per Insurance Policy Depreciation and amortization expense Depreciation, Depletion and Amortization Income Tax Disclosure [Abstract] Deferred tax assets: Deferred Tax Assets, Net [Abstract] Discount on loss reserves Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses Unearned premium reserve Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Unearned Premiums Reserve Bad debts Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Accrued bonuses Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Bonuses Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Long-term incentive compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Other Deferred Tax Assets, Other Gross deferred tax assets Deferred Tax Assets, Gross Valuation allowance for deferred tax assets Deferred Tax Assets, Valuation Allowance, Other Deferred Tax Assets, Valuation Allowance, Other Deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred tax liabilities: Deferred Tax Liabilities, Gross [Abstract] Deferred policy acquisition costs Deferred Tax Liabilities, Deferred Expense Investment securities – unrealized gains Deferred Tax Liabilities, Other Comprehensive Income Fixed assets Deferred Tax Liabilities, Property, Plant and Equipment Loss reserve transition liability Deferred Tax Liabilities, Loss Reserve Transition Liability Deferred Tax Liabilities, Loss Reserve Transition Liability Other Deferred Tax Liabilities, Other Net deferred tax assets Deferred Tax Liabilities, Gross Net deferred tax assets Deferred Tax Assets, Net Current income taxes Income Taxes Receivable (Payable), Current Income Taxes Receivable (Payable), Current Current and deferred income taxes Deferred Tax Assets, Net and Income Taxes Receivable, Current Deferred Tax Assets, Net and Income Taxes Receivable, Current Supplementary Insurance Information [Abstract] SCHEDULE III - SUPPLEMENTARY INSURANCE INFORMATION Supplementary Insurance Information, for Insurance Companies Disclosure [Text Block] Compensation and Retirement Disclosure [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Health care cost trend rate assumed for next fiscal year Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year Ultimate health care cost trend rate Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Year that rate reaches ultimate trend rate Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate Stockholders' Equity Note [Abstract] Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Change Postretirement Benefite Liability [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Unrealized Gains on Investments, net [Member] Accumulated Net Unrealized Gain (Loss) and Other-than-Temporary Impairment [Member] Accumulated Net Unrealized Gain (Loss) and Other-than-Temporary Impairment [Member] Reclassification Adjustment for Other-than-Temporary Impairment [Member] Accumulated Other-than-Temporary Impairment Attributable to Parent [Member] Accumulated Unrealized Gains on Investments, Net [Member] Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Before Tax [Abstract] Other Comprehensive Income (Loss), before Tax [Abstract] Accumulated other comprehensive income, beginning of period AOCI Including Portion Attributable to Noncontrolling Interest, before Tax Effect on other comprehensive income Other Comprehensive Income (Loss), before Tax Other comprehensive income before reclassification Other Comprehensive Income (Loss), before Reclassifications, before Tax Reclassification adjustment Reclassicification from Accumulated Other Comprehensive Income, Current Period, Before Tax Reclassicification from Accumulated Other Comprehensive Income, Current Period, Before Tax Accumulated other comprehensive income, end of period Income Tax [Abstract] Other Comprehensive Income (Loss), Tax [Abstract] Accumulated other comprehensive income, beginning of period Accumulated Other Comprehensive Income (Loss), Tax Accumulated Other Comprehensive Income (Loss), Tax Other comprehensive income before reclassification Other Comprehensive Income (Loss) before Reclassifications, Tax Reclassification adjustment Reclassicification from Accumulated Other Comprehensive Income, Current Period, Tax Reclassicification from Accumulated Other Comprehensive Income, Current Period, Tax Effect on other comprehensive income Other Comprehensive Income (Loss), Tax Accumulated other comprehensive income, end of period Net [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated other comprehensive income, beginning of period Accumulated Other Comprehensive Income (Loss), Net of Tax Reclassification adjustment Reclassicification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Reclassicification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Other comprehensive income before reclassification Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income, end of period Subsequent Events [Abstract] Subsequent Event Subsequent Events [Text Block] Insurance [Abstract] Short-duration Insurance Contracts, Historical Claims Duration [Table] Short-duration Insurance Contracts, Historical Claims Duration [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Personal Auto - Liability Property And Casualty, Personal Insurance Product Line, Liability [Member] Property And Casualty, Personal Insurance Product Line, Liability [Member] Personal Auto - Physical Damage Property And Casualty, Personal Insurance Product Line, Physical Damage [Member] Property And Casualty, Personal Insurance Product Line, Physical Damage [Member] Commercial Auto - Liability Property And Casualty, Commercial Insurance Product Line, Liability [Member] Property And Casualty, Commercial Insurance Product Line, Liability [Member] Commercial Auto - Physical Damage Property And Casualty, Commercial Insurance Product Line, Physical Damage [Member] Property And Casualty, Commercial Insurance Product Line, Physical Damage [Member] Short-duration Insurance Contracts, Historical Claims Duration [Line Items] Short-duration Insurance Contracts, Historical Claims Duration [Line Items] Year 1 Short-duration Insurance Contracts, Historical Claims Duration, Year One Year 2 Short-duration Insurance Contracts, Historical Claims Duration, Year Two Year 3 Short-duration Insurance Contracts, Historical Claims Duration, Year Three Year 4 Short-duration Insurance Contracts, Historical Claims Duration, Year Four Year 5 Short-duration Insurance Contracts, Historical Claims Duration, Year Five Year 6 Short-duration Insurance Contracts, Historical Claims Duration, Year Six Year 7 Short-duration Insurance Contracts, Historical Claims Duration, Year Seven Year 8 Short-duration Insurance Contracts, Historical Claims Duration, Year Eight Year 9 Short-duration Insurance Contracts, Historical Claims Duration, Year Nine Year 10 Short-duration Insurance Contracts, Historical Claims Duration, Year Ten Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Personal Auto Personal Auto Segment [Member] Personal Auto Segment [Member] Commercial Auto Commercial Vehicle Segment [Member] Commercial Vehicle Segment [Member] Classic Collector Classic Collector Segment [Member] Classic Collector Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Gross written premium Reinsurance Premiums for Insurance Companies, Direct Written Premium, Gross Amount Including Reinsurance Assumed Reinsurance Premiums for Insurance Companies, Direct Written Premium, Gross Amount Including Reinsurance Assumed Ceded reinsurance Reinsurance Premiums for Insurance Companies, Direct Written Premium, Amount Ceded to Other Companies Reinsurance Premiums for Insurance Companies, Direct Written Premium, Amount Ceded to Other Companies Net written premium Reinsurance Premiums for Insurance Companies, Direct Written Premium, Net Amount Reinsurance Premiums for Insurance Companies, Direct Written Premium, Net Amount Change in unearned premium Reinsurance Premiums for Insurance Companies, Direct Written Premium, Net Amount Increase (Decrease) Reinsurance Premiums for Insurance Companies, Direct Written Premium, Net Amount Increase (Decrease) Earned premium Premiums Earned, Net Installment and other fee income ipcc_InstallmentandOtherFeeIncome Installment and other fees collected from policyholders. Net investment income Net Investment Income Net realized gains on investments Other income Other Income Total revenues Revenues Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Investments by Unrealized Gain or Loss Position [Axis] Investments by Unrealized Gain or Loss Position [Axis] Investments by Unrealized Gain or Loss Position [Axis] Investments by Unrealized Gain or Loss Position [Domain] Investments by Unrealized Gain or Loss Position [Domain] Investments by Unrealized Gain or Loss Position [Domain] Securities with Unrealized Gains Securities with Unrealized Gains [Member] Securities with Unrealized Gains [Member] Securities with Unrealized Losses Securities with Unrealized Losses [Member] Securities with Unrealized Losses [Member] Securities with No Unrealized Gains or Losses Securities with No Unrealized Gains or Losses [Member] Securities with No Unrealized Gains or Losses [Member] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] One year or less, fair value Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value One year or less, amortized cost Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis After one year through five years, fair value Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value After one year through five years, amortized cost Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis After five years through ten years, fair value Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value After five years through ten years, amortized cost Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis After ten years, fair value Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value After ten years, amortized cost basis Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis Mortgage-backed, asset-backed and collateralized mortgage obligations, fair value Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value Mortgage-backed, asset-backed and collateralized mortgage obligations, amortized cost Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis Fixed maturities, amortized costs Available-for-sale Debt Securities, Amortized Cost Basis Nature of Operations Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Basis of Consolidation and Reporting Basis of Accounting, Policy [Policy Text Block] Estimates Use of Estimates, Policy [Policy Text Block] Investments Investment, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Reinsurance Reinsurance Accounting Policy [Policy Text Block] Advertising Advertising Cost, Policy, Expensed Advertising Cost [Policy Text Block] Deferred Policy Acquisition Costs (DPAC) Deferred Policy Acquisition Costs, Policy [Policy Text Block] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Unpaid Losses and Loss Adjustment Expense (LAE) Unpaid Policy Claims and Claims Adjustment Expense, Policy [Policy Text Block] Premium and Receivables Insurance Premiums Revenue Recognition, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Benefit Plans Pension and Other Postretirement Plans, Policy [Policy Text Block] Recently Adopted and Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Fair value of plan assets Defined Benefit Plan, Fair Value of Plan Assets Benefit obligation Defined Benefit Plan, Benefit Obligation Funded status at end of year Defined Benefit Plan, Funded Status of Plan Contributions made after the measurement date Defined Benefit Plan, Contributions After the Measurement Date Defined Benefit Plan, Contributions After the Measurement Date Unrecognized actuarial net (gain) loss Defined Benefit Plan, Unrecognized Actuarial Gain (Loss), Net Defined Benefit Plan, Unrecognized Actuarial Gain (Loss), Net Unrecognized prior service cost Defined Benefit Plan, Unrecognized Prior Service Cost (Credit) Defined Benefit Plan, Unrecognized Prior Service Cost (Credit) Long-term Debt Long-term Debt [Text Block] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Current Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit) Provision for income taxes Income Tax Expense (Benefit) Schedule of Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Schedule of net benefit obligation Schedule of Changes in Projected Benefit Obligations [Table Text Block] Schedule of weighted-average assumptions used Schedule of Assumptions Used [Table Text Block] Schedule of net benefit costs Schedule of Net Benefit Costs [Table Text Block] Schedule of health care cost trend rates Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block] Schedule of changes in fair value of plan assets Schedule of Changes in Fair Value of Plan Assets [Table Text Block] Schedule of amounts recognized in balance sheet Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Schedule of expected benefit payments Schedule of Expected Benefit Payments [Table Text Block] Liability for unpaid losses and LAE Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Schedule of incurred losses and cumulative paid claims for prior ten accident years Short-duration Insurance Contracts, Claims Development [Table Text Block] Reconciliation of net incurred and paid development tables to liability for unpaid losses and LAE Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block] Schedule of average annual payout of incurred losses and ALAE Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block] Consolidated Statements of Earnings [Abstract] Consolidated Statements of Earnings [Abstract] Revenues: Revenues [Abstract] Earned premium, percent change Increase Decrease in Premiums Earned, Net, Property And Casualty Increase Decrease in Premiums Earned, Net, Property And Casualty Installment and other fee income, percent change Increase Decrease Installment and Other Fee Income Increase Decrease Installment and Other Fee Income Net investment income, percent change Increase Decrease in Net Investment Income Increase Decrease in Net Investment Income Net realized gains on investments Net realized gains on investments, percent change Increase Decrease Realized Investment Gains Losses Increase Decrease Realized Investment Gains Losses Other income, percent change Increase Decrease in Other Income Increase Decrease in Other Income Total revenues, percent change Increase Decrease in Revenues Increase Decrease in Revenues Costs and Expenses: Costs and Expenses [Abstract] Losses and loss adjustment expenses Policyholder Benefits and Claims Incurred, Net, Property, Casualty and Liability Losses and loss adjustment expense, percent change Increase Decrease in Incurred Claims Property Casualty And Liability Increase Decrease in Incurred Claims Property Casualty And Liability Commissions and other underwriting expenses Commissions and Other Underwriting Expenses Commission expense incurred to persons or entities for generating or placing insurance policies with the company, determined as percentage of policy premiums, as well as costs incurred during the period, such as those relating to general administration and policy maintenance, that do not vary with and are not primarily related to the acquisition or renewal of insurance contracts. Commissions and other underwriting expenses, percent change Increase Decrease in Commissions And Other Underwriting Expenses Increase Decrease in Commissions And Other Underwritting Expenses Interest expense Interest Expense Interest expense, percent change Increase Decrease in Interest Expense Increase Decrease in Interest Expense Corporate general and administrative expenses General and Administrative Expense Corporate general and administrative expenses, percent change Increase Decrease in General and Administrative Expense Increase Decrease in General and Administrative Expense Other expenses Other Cost and Expense, Operating Other expenses, percent change Increase Decrease in Other Cost and Expense Operating Increase Decrease in Other Cost and Expense Operating Total costs and expenses Benefits, Losses and Expenses Total costs and expenses, percent change Increase Decrease in Benefits Losses and Expenses Increase Decrease in Benefits Losses and Expenses Earnings before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Earnings before income taxes, percent change Increase Decrease in Income Loss from Continuing Operations Before Income Taxes Minority Interest and Inome Loss from Equity Method Investments Increase Decrease in Income Loss from Continuing Operations Before Income Taxes Minority Interest and Inome Loss from Equity Method Investments Income Taxes Provision for income taxes Provision for income taxes, percent change Increase Decrease in Income Tax Expense Benefit Increase Decrease in Income Tax Expense Benefit Net Earnings Net Earnings, percent change Increase Decrease in Net Income Loss Increase Decrease in Net Income Loss Net Earnings per Common Share: Earnings Per Share [Abstract] Basic earnings per share (usd per share) Earnings Per Share, Basic Basic earnings per share, percent change Increase Decrease in Earnings Per Share Basic Increase Decrease in Earnings Per Share Basic Diluted earnings per share (usd per share) Earnings Per Share, Diluted Diluted earnings per share, percent change Increase Decrease in Earnings Per Share Diluted Increase Decrease in Earnings Per Share Diluted Average Number of Common Shares: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic average number of common shares Weighted Average Number of Shares Outstanding, Basic Basic average number of common shares, percent change Increase Decrease in Weighted Average Number of Shares Outstanding Basic Increase Decrease in Weighted Average Number of Shares Outstanding Basic Diluted average number of common shares Weighted Average Number of Shares Outstanding, Diluted Diluted average number of common shares, percent change Increase Decrease in Weighted Average Number of Diluted Shares Outstanding Increase Decrease in Weighted Average Number of Diluted Shares Outstanding Cash Dividends per Common Share (usd per share) Common Stock, Dividends, Per Share, Cash Paid Cash Dividends per Common Share, percent change Increase Decrease in Common Stock Dividends Per Share Cash Paid Increase Decrease in Common Stock Dividends Per Share Cash Paid Net realized gains before impairment losses Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments Net realized gains before impairment losses, percent change Increase Decrease in Avaiable for Sale Securities Gross Realized Gain Loss Excluding Other than Temporary Impairments Increase Decrease in Avaiable for Sale Securities Gross Realized Gain Loss Excluding Other than Temporary Impairments Total other-than-temporary impairment (OTTI) losses Other than Temporary Impairment Losses, Investments, Available-for-sale Securities Total other-than-temporary impairment (OTTI) losses, percent change Increase Decrease in Impairment Losses Investment Available for Sale Securities Increase Decrease in Impairment Losses Investment Available for Sale Securities Non-credit portion in other comprehensive income Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities OTTI losses reclassified from other comprehensive income Impairment Loss Reclassified From Other Comprehensive Income To Earnings Other-than-temporary impairment losses reclassed from other comprehensive income to earnings. OTTI losses reclassified from other comprehensive income, percent change Increase Decrease in Impairment Loss Reclassified from Other Comprehensive Income To Earnings Increase Decrease in Impairment Loss Reclassified from Other Comprehensive Income To Earnings Net impairment losses recognized in earnings Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities Net impairment losses recognized in earnings, percent change Increase Decrease in Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net Available for Sale Securities Increase Decrease in Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net Available for Sale Securities Commitments and Contingencies Disclosure [Abstract] Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Automobiles [Member] Automobiles [Member] Entity by Location [Axis] Entity by Location [Axis] Location [Domain] Location [Domain] Birmingham, Alabama [Member] Miami, Florida [Member] Miami, Florida [Member] Los Angeles, California [Member] Los Angeles, California [Member] Los Angeles, California [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2017 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2018 Operating Leases, Future Minimum Payments, Due in Two Years 2019 Operating Leases, Future Minimum Payments, Due in Three Years 2020 Operating Leases, Future Minimum Payments, Due in Four Years 2021 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Operating leases, lease expiration period Operating Leases, Lease Expiration, Term Operating Leases, Lease Expiration, Term Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2017 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2018 Capital Leases, Future Minimum Payments Due in Two Years 2019 Capital Leases, Future Minimum Payments Due in Three Years 2020 Capital Leases, Future Minimum Payments Due in Four Years 2021 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total Capital Leases, Future Minimum Payments Due Lease expense Operating Leases, Rent Expense Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Investment [Axis] Investment [Axis] Investment [Domain] Investment [Domain] Rabbi Trust [Member] Rabbi Trust [Member] Rabbi Trust [Member] Proceeds from sale of securities Proceeds from Sale of Available-for-sale Securities Receivable for securities sold Receivable for Investments Sold Receivable For Investments Sold Gross realized gains on sale of securities Available-for-sale Securities, Gross Realized Gains Gross realized losses on sale of securities Available-for-sale Securities, Gross Realized Losses Statutory accident year underwriting income Statutory Accounting Practices, Statutory Underwriting Income (Loss), Amount Statutory Accounting Practices, Statutory Underwriting Income (Loss), Amount Statutory accident year underwriting income, Combined Ratio Statutory Accounting Practices, Statutory Underwriting Income (Loss), Combined Ratio Statutory Accounting Practices, Statutory Underwriting Income (Loss), Combined Ratio Bad debt charge-offs Premiums Receivable, Allowance for Doubtful Accounts, Write Offs Against Allowance Favorable (unfavorable) development on prior accident years Prior Year Claims and Claims Adjustment Expense Statutory calendar year underwriting income Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Amount Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Amount Statutory calendar year underwriting income, Combined Ratio Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Combined Ratio Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Combined Ratio Statutory-to-GAAP underwriting income differences Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Differences Statutory Accounting Practices, Statutory To GAAP, Underwriting Income (Loss), Differences GAAP calendar year underwriting income Statutory Accounting Practices, Statutory To GAAP, GAAP Underwriting Income (Loss), Amount Statutory Accounting Practices, Statutory To GAAP, GAAP Underwriting Income (Loss), Amount GAAP calendar year underwriting income, Combined Ratio Statutory Accounting Practices, Statutory To GAAP, GAAP Underwriting Income (Loss), Combined Ratio Statutory Accounting Practices, Statutory To GAAP, GAAP Underwriting Income (Loss), Combined Ratio Interest expense Corporate general and administrative expenses Other expenses Schedule of Shares Issued by Plan Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Severity of Unrealized Loss [Axis] Severity of Unrealized Loss [Axis] Severity of Unrealized Loss [Axis] Severity of Unrealized Loss [Domain] Severity of Unrealized Loss [Domain] Severity of Unrealized Loss [Domain] Less Than 5% as a Percentage of Amortized Cost or Cost Less Than Five Percent as a Percentage of Amortized Cost or Cost [Member] Less Than Five Percent as a Percentage of Amortized Cost or Cost [Member] 5% - 10% as a Percentage of Amortized Cost or Cost Between Five Percent and Ten Percent as a Percentage of Amortized Cost or Cost [Member] Between Five Percent and Ten Percent as a Percentage of Amortized Cost or Cost [Member] Greater Than 10% as a Percentage of Amortized Cost or Cost Greater Than Ten Percent as a Percentage of Amortized Cost or Cost [Member] Greater Than Ten Percent as a Percentage of Amortized Cost or Cost [Member] Age of Unrealized Loss [Axis] Age of Unrealized Loss [Axis] Age of Unrealized Loss [Axis] Age of Unrealized Loss [Domain] Age of Unrealized Loss [Domain] Age of Unrealized Loss [Domain] 0-3 months Zero To Three Months [Member] Zero To Three Months [Member] 3-6 months Three To Six Months [Member] Three To Six Months [Member] 6-9 months Six To Nine Months [Member] Six To Nine Months [Member] 9-12 months Nine To Twelve Months [Member] Nine To Twelve Months [Member] Greater than twelve months Greater Than Twelve Months [Member] Greater Than Twelve Months [Member] Fair Value of Securities with Unrealized Losses, 0-12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Fair Value of Securities with Unrealized Losses, Greater Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Fair Value of Securities with Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Total Gross Unrealized Losses, 0-12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Total Gross Unrealized Losses, Greater Than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Gross Unrealized Losses Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Fair Value Disclosures [Abstract] 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Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Total cash and investments Schedule of future minimum rental payments for operating leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Rent Expense Schedule of Rent Expense [Table Text Block] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Forecast Scenario, Forecast [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Officers Officer [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Restricted stock Restricted Stock [Member] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Nonvested options, beginning balance (in shares) 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Other Postretirement Benefits Disclosure [Text Block] Restricted Stock Plan Restricted Stock Plan [Member] Restricted Stock Plan [Member] Directors Plan Directors Plan [Member] Directors Plan [Member] ESPP Employee Stock Purchase Plan (ESPP) [Member] Employee Stock Purchase Plan (ESPP) [Member] PSP Performance Share Plan (PSP) [Member] Performance Share Plan (PSP) [Member] Expense Recognized in Earnings Allocated Share-based Compensation Expense Tax Benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Reconciliation of provision for income taxes Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Components of income tax expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Significant Reporting and Accounting Policies Significant Accounting Policies [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Senior Notes Due 2022 Senior Notes Due 2022 [Member] Senior Notes Due 2022 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Principal Debt Instrument, Face Amount Unamortized debt issuance costs Debt Issuance Costs, Net Long-term debt less unamortized debt issuance costs Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income, Net of Tax AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance Net change in post-retirement benefit liability Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Change in unrealized gain on investments Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax, Excluding Other Than Temporary Impairment Portion Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax, Excluding Other Than Temporary Impairment Portion Change in non-credit component of impairment losses on fixed maturities Non Credit Portion Of Other Than Temporary Impairments Recognized In Other Comprehensive Income Non-Credit Portion of Other-Than-Temporary Impairments Recognized in Other Comprehensive Income Dividends paid to common shareholders Dividends, Common Stock, Cash Shares issued and share-based compensation expense, including tax benefit Stock Issued During Period Value Value of stock issued during the period as a result of any share-based compensation plan. Acquisition of treasury stock Treasury Stock, Value, Acquired, Par Value Method Ending Balance Schedule of Segment Revenues and Earnings Before Income Taxes Schedule of Segment Reporting Information, by Segment [Table Text Block] Equity in consolidated subsidiaries Income (Loss) from Subsidiaries, before Tax Excess tax benefits from share-based payment arrangements Other Other Operating Activities, Cash Flow Statement Dividends received from subsidiary Cash Dividends Paid to Parent Company Securities received from subsidiaries Securities, Paid to Parent Company Securities, Paid to Parent Company Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Reinsurance Premiums for Insurance Companies, by Product Segment [Table] Involuntary Pools and Associations [Member] Involuntary Pools and Associations [Member] Involuntary Pools and Associations [Member] Commercial Auto Insurance [Member] Commercial Auto Insurance [Member] Commercial Auto Insurance [Member] Extra-Contractual Loss Reinsurance [Member] Extra-Contractual Loss Reinsurance [Member] Extra-Contractual Loss Reinsurance [Member] Insurance Type and Tier Identifier [Axis] Insurance Type and Tier Identifier [Axis] Type and Tier Identifier [Domain] Type and Tier Identifier [Domain] General liability [Member] General Liability [Member] Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items] Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items] Liability for unpaid losses and LAE Assumed Liability for Unpaid Claims and Claims Adjustment Expense Amount assumed from other companies (less than) Assumed Premiums Earned Catastrophe reinsurance, additional coverage, third party recovery, percentage Catastrophe Reinsurance, Additional Coverage, Third Party Recovery, Percentage Catastrophe Reinsurance, Additional Coverage, Third Party Recovery, Percentage Additional coverage, loss coverage base per event Catastrophe Reinsurance, Additional Coverage, Loss Coverage Base Per Event Catastrophe Reinsurance, Additional Coverage, Loss Coverage Base Per Event Additional coverage, minimum loss threshold per event Catastrophe Reinsurance, Additional Coverage, Minimum Loss Threshold Per Event Catastrophe Reinsurance, Additional Coverage, Minimum Loss Threshold Per Event Property catastrophe reinsurance, first layer Property Catastrophe Reinsurance First Layer Property Catastrophe Reinsurance, First Layer First layer percentage reinsured Property Catastrophe Reinsurance, First Layer Percentage Property Catastrophe Reinsurance, First Layer Percentage Remaining layers percentage reinsured Property Catastrophe Reinsurance, Remaining Layers Percentage Property Catastrophe Reinsurance, Remaining Layers Percentage Maximum third party recovery Catastrophe Reinsurance, Maximum Third Party Recovery Catastrophe Reinsurance, Maximum Third Party Recovery Minimum loss threshold per event Catastrophe Reinsurance, Minimum Loss Threshold Per Event Catastrophe Reinsurance, Minimum Loss Threshold Per Event Quota share for general liability Reinsurance Quota Share, Percentage Reinsurance Quota Share, Percentage Unearned premium returned due to termination of excess loss contract Ceded Premiums Earned, Unearned Premium Offset Due to Termination of Excess Loss Contract Ceded Premiums Earned, Unearned Premium Offset Due to Termination of Excess Loss Contract Ceding commissions Ceded Premiums Earned, Ceding Commissions Ceded Premiums Earned, Ceding Commissions on Unearned Premium Reduction in losses due to amount ceded to other companies Policyholder Benefits and Claims Incurred, Ceded Discount from market price on purchase date Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date Maximum percentage of employee base salary