Statistical Measurement [Domain]
Statistical Measurement [Domain]
Schedule of Other Information Regarding Available-For-Sale Securities
Debt Securities, Available-for-Sale [Table Text Block]
Medical Technology Liability
Medical Technology and Life Sciences Product Liability [Member]
Medical Technology and Life Sciences Product Liability
(Favorable) unfavorable development of reserves established in prior years, net
Prior Year Claims and Claims Adjustment Expense
Award Timing Predetermined
Award Timing Predetermined [Flag]
Deferred policy acquisition costs and amortization
Deferred Policy Acquisition Costs, Amortization Expense, Excluding Accrued Interest
Entity File Number
Entity File Number
Additional Paid-in Capital
Additional Paid-in Capital [Member]
Cash Flow Hedge- Interest Rate Swaps
Interest Rate Swap [Member]
Valuation Approach and Technique [Domain]
Valuation Approach and Technique [Domain]
Included in other comprehensive income (loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)
Tabular List, Table
Tabular List [Table Text Block]
Unearned premiums
Unearned Premiums
Accounting Changes Adopted and Accounting Changes Not Yet Adopted
New Accounting Pronouncements, Policy [Policy Text Block]
Pledged Status [Axis]
Pledged Status [Axis]
Schedule of Financial Instruments Not Measured at Fair Value
Fair Value, by Balance Sheet Grouping [Table Text Block]
Prior year claims and claims adjustment expense, purchase accounting amortization
Prior Year Claims and Claims Adjustment Expense, Purchase Accounting Amortization
Prior Year Claims and Claims Adjustment Expense, Purchase Accounting Amortization
Fixed maturities
Debt Securities [Member]
Gross Unrealized Losses
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax
Trading Arrangements, by Individual
Trading Arrangements, by Individual [Table]
Measurement Basis [Axis]
Measurement Basis [Axis]
Basic (in usd per share)
Earnings Per Share, Basic
Adjustment to Compensation:
Adjustment to Compensation [Axis]
Named Executive Officers, Footnote
Named Executive Officers, Footnote [Text Block]
Liabilities:
Liabilities, Fair Value Disclosure [Abstract]
Term Loan
Term Loan [Member]
Term Loan
Other comprehensive income (loss)
Other Comprehensive Income (Loss), Net of Tax
Schedule of Segment Reporting Information, by Segment
Schedule of Segment Reporting Information, by Segment [Table Text Block]
Securities sold during the period
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Securities Sold
Current expense (benefit)
Current Income Tax Expense (Benefit)
Measurement Input Type [Domain]
Measurement Input Type [Domain]
Schedule of Available-For-Sale Fixed Maturities
Schedule of Available-for-Sale Securities Reconciliation [Table Text Block]
Adjustment to Compensation, Amount
Adjustment to Compensation Amount
Change in unrealized gains (losses) included in earnings
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)
Other assets
Increase (Decrease) in Other Operating Assets
Share-based compensation
Share-Based Payment Arrangement, Noncash Expense
Aggregate Notional Amount
Derivative Asset, Notional Amount
Proceeds from sale of intangible assets
Proceeds from Sale of Intangible Assets
Employee Stock Option
Share-Based Payment Arrangement, Option [Member]
Award Timing MNPI Disclosure
Award Timing MNPI Disclosure [Text Block]
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity, Primary Beneficiary [Member]
Unrealized Investment Gains (Losses)
AOCI, Gain (Loss), Debt Securities, Available-for-Sale, without Allowance for Credit Loss, Parent [Member]
Total Shareholders' Equity
Beginning balance
Ending balance
Equity, Attributable to Parent
OCI, before reclassifications, net of tax
OCI, before Reclassifications, Net of Tax, Attributable to Parent
Debt Securities, Available-for-sale [Table]
Debt Securities, Available-for-Sale [Table]
Measurement Frequency [Axis]
Measurement Frequency [Axis]
Insider Trading Policies and Procedures [Line Items]
Schedule of a Roll Forward of Cumulative Credit Losses Recorded in Earnings Related to Impaired Debt Securities
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Table Text Block]
Common shares, shares authorized (in shares)
Common Stock, Shares Authorized
Tax Period [Domain]
Tax Period [Domain]
Number of limited partners not permitted for redemption
Number of Limited Partners not Permitted for Redemption
Number of Limited Partners Not Permitted for Redemption
Financial assets:
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Total Liabilities and Shareholders' Equity
Liabilities and Equity
Recurring
Fair Value, Recurring [Member]
Unrecognized Change in Defined Benefit Plan Liabilities
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Deferred policy acquisition costs
Deferred Policy Acquisition Cost
Liabilities and Shareholders' Equity
Liabilities and Equity [Abstract]
Distributed earnings from unconsolidated subsidiaries
Return On Invested Capital From Unconsolidated Subsidiaries
Return On Invested Capital From Unconsolidated Subsidiaries
Premiums receivable, net (allowance for expected credit losses, $8,049 and $8,141, respectively)
Premiums Receivable, Net
Cover [Abstract]
Cover [Abstract]
Amounts reclassified from AOCI, net of tax
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent
Portion at Fair Value Measurement
Portion at Fair Value Measurement [Member]
Other Limited Partnerships and Limited Liability Company, Greater Than 25% Ownership
Other Limited Partnerships and Limited Liability Company, Greater Than 25 Percent Ownership [Member]
Other Limited Partnerships and Limited Liability Company, Greater Than 25 Percent Ownership [Member]
Maximum
Maximum
Maximum [Member]
Schedule of Credit Derivatives [Table]
Credit Derivative [Table]
Schedule of Equity Method Investments [Table]
Equity Method Investment [Table]
Fair Value
Debt Securities, Available-for-Sale, Unrealized Loss Position
Tax Year 2019
Tax Year 2019 [Member]
Non-PEO NEO Average Total Compensation Amount
Non-PEO NEO Average Total Compensation Amount
Debt Instrument [Line Items]
Debt Instrument [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets held at period-end
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)
Other investments
Payments to Acquire Other Investments
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]
Treasury Stock
Treasury Stock, Common [Member]
Adjustment to Non-PEO NEO Compensation Footnote
Adjustment to Non-PEO NEO Compensation Footnote [Text Block]
Pay vs Performance Disclosure [Line Items]
Operating lease liabilities
Operating Lease, Liability
Unearned premiums
Increase (Decrease) in Unearned Premiums
Comparability Adjustment
Measurement Input, Comparability Adjustment [Member]
Forgone Recovery due to Disqualification of Tax Benefits, Amount
Forgone Recovery due to Disqualification of Tax Benefits, Amount
Liabilities
Liabilities [Abstract]
Non-Rule 10b5-1 Arrangement Terminated
Non-Rule 10b5-1 Arrangement Terminated [Flag]
Number of corporate bonds
Impairment Loss, Debt Securities, Number Of Corporate Bonds
Impairment Loss, Debt Securities, Number Of Corporate Bonds
Entity Shell Company
Entity Shell Company
Schedule of Long-term Debt Instruments [Table]
Schedule of Long-Term Debt Instruments [Table]
Proceeds from sale of property
Proceeds from Sale of Property, Plant, and Equipment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reserve for losses and loss adjustment expenses
Increase (Decrease) in Liability for Claims and Claims Adjustment Expense Reserve
Statement of Stockholders' Equity [Abstract]
Statement of Stockholders' Equity [Abstract]
Operating segments
Operating Segments [Member]
Schedule of Variable Interest Entities [Table]
Variable Interest Entity [Table]
Statement of Cash Flows [Abstract]
Statement of Cash Flows [Abstract]
Intangible assets, net
Other Intangible Assets, Net
Company Selected Measure Amount
Company Selected Measure Amount
Award Timing MNPI Considered
Award Timing MNPI Considered [Flag]
Interest expense
Interest expense
Interest Expense, Operating
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Comprehensive income (loss)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Measurement Input Type [Axis]
Measurement Input Type [Axis]
Name
Measure Name
Payment period for redemption of LP valued at NAV
Payment Period for Redemption of LP Valued at NAV
The number of days required for payment upon redemption of a particular LP that is valued at NAV.
Document Fiscal Period Focus
Document Fiscal Period Focus
No impairment has been previously recognized
Impairment Loss, Debt Securities, No Impairment Previously Recognized
Impairment Loss, Debt Securities, No Impairment Previously Recognized
Award Timing Method
Award Timing Method [Text Block]
Industrial
Equity Industrial Securities [Member]
Equity securities in financial sector.
Net favorable development in workers' compensation business
Net Favorable Development in Workers' Compensation Business
Net Favorable Development in Workers' Compensation Business
Award Type [Axis]
Award Type [Axis]
Policy liabilities and accruals
Policy liabilities and accruals [Abstract]
Policy liabilities and accruals.
Tax Credit Partnerships Less Than 20% Ownership
Tax Credit Partnerships Less Than 20% Ownership [Member]
Tax Credit Partnerships Less Than 20% Ownership [Member]
Debt less unamortized debt issuance costs
Debt less unamortized debt issuance costs
Long-Term Debt
Legal Entity [Axis]
Legal Entity [Axis]
Policy acquisition costs, net of amortization (net deferral)
Increase (Decrease) in Deferred Policy Acquisition Costs
Total Assets
VIEs carrying value
Assets
Investment, Name [Domain]
Investment, Name [Domain]
Trading Symbol
Trading Symbol
Operating expenses
Underwriting Policy Acquisition And Operating Expense
Underwriting, policy acquisition and operating expense.
Non-credit Impairments
AOCI, Gain (Loss), Debt Securities, Available-for-Sale, with Allowance for Credit Loss, Parent [Member]
Entity Address, City or Town
Entity Address, City or Town
Operating Activities
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Change in unrealized holding gains (losses), trading fixed maturities
Debt Securities, Trading, Unrealized Gain (Loss)
Non-PEO NEO Average Compensation Actually Paid Amount
Non-PEO NEO Average Compensation Actually Paid Amount
Investment in unconsolidated subsidiaries
Investments In Unconsolidated Subsidiaries [Member]
Investments In Unconsolidated Subsidiaries [Member]
Restricted Share Units
Restricted Stock Units (RSUs) [Member]
Income Statement Location [Domain]
Statement of Income Location, Balance [Domain]
Non-public equity funds
Private Equity Funds [Member]
Net impairment losses recognized in earnings
Net impairment losses recognized in earnings
Net impairment losses recognized in earnings
Impairment Loss, Debt Securities, Portion Recognized in Earnings
Impairment Loss, Debt Securities, Portion Recognized in Earnings
Compensation Actually Paid vs. Other Measure
Compensation Actually Paid vs. Other Measure [Text Block]
SPC dividend expense (income)
SPC dividend (expense) income
Segregated Portfolio Cells Dividend Expense (Income)
Segregated Portfolio Cells Dividend Expense (Income)
Assets:
Assets:
Assets, Fair Value Disclosure [Abstract]
Variable Interest Entity [Line Items]
Variable Interest Entity [Line Items]
Entity Emerging Growth Company
Entity Emerging Growth Company
Entity Common Stock, Shares Outstanding (in shares)
Entity Common Stock, Shares Outstanding
Operating lease liabilities arising from obtaining ROU assets
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability
Debt Securities, Available-for-Sale [Line Items]
Debt Securities, Available-for-Sale [Line Items]
Borrowings (repayments) under Revolving Credit Agreement
Repayments of Lines of Credit
Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year
Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member]
Prepaid reinsurance premiums
Prepaid Reinsurance Premiums
Level 2
Fair Value, Inputs, Level 2 [Member]
Insider Trading Policies and Procedures Not Adopted
Insider Trading Policies and Procedures Not Adopted [Text Block]
Business Combination [Domain]
Business Combination [Domain]
Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases
Asset Pledged as Collateral
Asset Pledged as Collateral [Member]
Reinsurance related assets and liabilities
Increase (Decrease) In Reinsurance Related Assets And Liabilities
The change in reinsurance related assets and liabilities on the balance sheet.
Insurance [Abstract]
Insurance [Abstract]
Other assets
Other assets
Other Assets, Fair Value Disclosure
PEO
PEO [Member]
Transfers in
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3
Tax credits recognized
Investment Program, Proportional Amortization Method, Elected, Income Tax Credit and Other Income Tax Benefit, before Amortization Expense
All other investments, primarily investment fund LPs/LLCs
Other Limited Partnerships and Limited Liability Company [Member]
Other Limited Partnerships and Limited Liability Company [Member]
Schedule of Available-For-Sale Securities by Contractual Maturity
Investments Classified by Contractual Maturity Date [Table Text Block]
Fixed maturities, trading, at fair value (cost, $12,971 and $52,493, respectively)
Fixed maturities, trading
Debt Securities, Trading
Significant Non-Cash Transactions
Noncash Investing and Financing Items [Abstract]
Due in one year or less
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value
Fair value, net asset (liability)
Fair Value, Net Asset (Liability)
Change in:
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]
Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year
Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member]
Nature of Operation, Product Information, Concentration of Risk [Table]
Nature of Operation, Product Information, Concentration of Risk [Table]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Additional credit losses recognized during the period, related to securities for which:
Additional Credit Losses Recognized During the Period, Related to Securities [Abstract]
Additional Credit Losses Recognized During the Period, Related to Securities
Retained Earnings
Retained Earnings [Member]
Total paid
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid
Effective interest rate on debt
Debt Instrument, Interest Rate, Effective Percentage
Pledged Status [Domain]
Pledged Status [Domain]
Fair Value Asset Recurring Basis Still Held Unrealized Gain Loss Statement Of Income Extensible List Not Disclosed Flag
Fair Value Asset Recurring Basis Still Held Unrealized Gain Loss Statement Of Income Extensible List Not Disclosed Flag
Fair Value Asset Recurring Basis Still Held Unrealized Gain Loss Statement Of Income Extensible List Not Disclosed Flag
Entity Address, Postal Zip Code
Entity Address, Postal Zip Code
Restatement Determination Date
Restatement Determination Date
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation
Estimated fair value
Derivative Asset
Total income tax expense (benefit)
Income tax expense (benefit)
Income Tax Expense (Benefit)
12 months or longer, Fair Value
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer
Basis spread on variable rate for debt
Debt Instrument, Basis Spread on Variable Rate
Right to receive cash per share of common stock converted (in USD per share)
Business Combination, Common Stock Conversion, Per Share
Business Combination, Common Stock Conversion, Per Share
Purchases of:
Payments to Acquire Investments [Abstract]
Interest Expense
Interest Expense [Member]
Other assets
Other Assets
Fair Value, Nonrecurring
Fair Value, Nonrecurring [Member]
Beginning balance
Ending balance
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value
Short-term and other investments
Investments, Fair Value Disclosure
Pension Adjustments Service Cost
Pension Adjustments Service Cost [Member]
Product and Service [Domain]
Product and Service [Domain]
Fair Value Hierarchy and NAV [Axis]
Fair Value Hierarchy and NAV [Axis]
Transfers out
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3
Net losses:
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Effect of dilutive shares on earnings (loss) per share (in usd per share)
Income (Loss) from Continuing Operations, Per Diluted Share
Net investment income
Net investment income
Net investment income
Net Investment Income
Equity securities measured at fair value
Equity Securities, FV-NI, Measurement Input
Restatement does not require Recovery
Restatement Does Not Require Recovery [Text Block]
Total liabilities categorized within the fair value hierarchy
Liabilities, Fair Value Disclosure
Derivative, notional amount
Derivative, Notional Amount
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net cash impact of deconsolidation of closed years of account from Lloyd's Syndicates operations
Closed Block Operations, Net Results
Purchases of capital assets
Payments to Acquire Other Productive Assets
Total gains (losses) realized and unrealized:
Gains Losses Realized and Unrealized Liabilities [Abstract]
Gains Losses Realized and Unrealized Liabilities
Underwriting, policy acquisition and operating expenses:
Underwriting, Policy Acquisition And Operating Expenses [Abstract]
Underwriting, Policy Acquisition And Operating Expenses [Abstract]
Compensation Actually Paid vs. Company Selected Measure
Compensation Actually Paid vs. Company Selected Measure [Text Block]
City Area Code
City Area Code
Award Timing, How MNPI Considered
Award Timing, How MNPI Considered [Text Block]
Receivable from reinsurers on paid losses and loss adjustment expenses
Reinsurance Recoverable for Paid Claims and Claims Adjustments
All Trading Arrangements
All Trading Arrangements [Member]
Equity Awards Adjustments, Footnote
Equity Awards Adjustments, Footnote [Text Block]
Total Shareholder Return Vs Peer Group
Total Shareholder Return Vs Peer Group [Text Block]
Schedule of Investment in Unconsolidated Subsidiaries
Schedule Of Investments In Unconsolidated Subsidiaries [Table Text Block]
Schedule Of Investments In Unconsolidated Subsidiaries [Table Text Block]
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Abstract]
Reinsurance premiums payable
Reinsurance Payable
Segment results
Segment Profit (Loss)
Segment Profit (Loss)
Utilities/Energy
Utilities Energy Equity Securities [Member]
Equity securities in the utilities and energy sectors.
Investing Activities
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Pay vs Performance Disclosure
Pay vs Performance Disclosure [Table]
Net cash provided (used) by operating activities
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation
Proceeds from sales (exclusive of maturities and paydowns)
Proceeds from Sale of Debt Securities, Available-for-Sale
Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments [Line Items]
Equity investments
Equity Securities, FV-NI
Other liabilities
Other Liabilities
Goodwill
Goodwill
Equity Valuation Assumption Difference, Footnote
Equity Valuation Assumption Difference, Footnote [Text Block]
Current year
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year
PEO Total Compensation Amount
PEO Total Compensation Amount
Long-term Debt, Type [Axis]
Long-Term Debt, Type [Axis]
Total net investment gains (losses)
Gain (Loss) on Investments
BOLI
BOLI
Cash Surrender Value [Member]
Tax credit carryforwards, expected recapture
Tax Credit Carryforward Amount, Expected Recapture
Tax Credit Carryforward Amount, Expected Recapture
Income taxes receivable
Income Taxes Receivable
Equity Components [Axis]
Equity Components [Axis]
Equity Components [Axis]
Transfers out
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3
Non-Rule 10b5-1 Arrangement Adopted
Non-Rule 10b5-1 Arrangement Adopted [Flag]
Number of reportable segments
Number of Reportable Segments
Available for sale securities, amortized cost
Amortized Cost
Amortized Cost
Debt Securities, Available-for-Sale, Amortized Cost
Net losses and loss adjustment expenses
Net losses and loss adjustment expenses
Policyholder Benefits and Claims Incurred, Net
Variable Interest Entities
Variable Interest Entity Disclosure [Text Block]
Other Performance Measure, Amount
Other Performance Measure, Amount
Entity Address, State or Province
Entity Address, State or Province
Interest and dividend income, operating
Interest and Dividend Income, Operating
Debt Securities, Available-for-sale, Allowance for Credit Loss [Table]
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Table]
Derivative Instrument [Axis]
Derivative Instrument [Axis]
Individual:
Individual [Axis]
Financial liabilities:
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Additional paid-in capital
Additional Paid in Capital, Common Stock
Investments
Investments [Abstract]
Entity [Domain]
Entity [Domain]
Net cash provided (used) by investing activities
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation
Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table
Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member]
Document Fiscal Year Focus
Document Fiscal Year Focus
Basis of Presentation
Basis of Accounting, Policy [Policy Text Block]
Operating lease ROU assets
Operating Lease, Right-of-Use Asset
Forgone Recovery, Explanation of Impracticability
Forgone Recovery, Explanation of Impracticability [Text Block]
Fair value of funded deferred compensation assets
Deferred Compensation Plan Assets
Entity Interactive Data Current
Entity Interactive Data Current
Other Limited Partnerships and Limited Liability Company Less than 25% Ownership
Other Limited Partnerships and Limited Liability Company Less than 25 Percent Ownership [Member]
Other Limited Partnerships and Limited Liability Company Less than 25 Percent Ownership [Member]
Carrying Value
Reported Value Measurement [Member]
Transaction-related costs, net
Business Combination, Acquisition-Related Cost, Expense
Equity [Abstract]
Equity [Abstract]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Net realized gains (losses), other investments
Other Investments, Realized Gain (Loss)
This item represents the gain (loss) realized during the period from the sale of Other Investments.
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]
Net investment gains (losses)
Gain (Loss) On Investments, Excluding Business Combination, Contingent Consideration Arrangements, Change In Amount Of Contingent Consideration, Liability
Gain (Loss) On Investments, Excluding Business Combination, Contingent Consideration Arrangements, Change In Amount Of Contingent Consideration, Liability
Credit funds
Structured Credit Fund [Member]
Investment LPs/LLCs that seek to obtain superior risk-adjusted absolute returns by acquiring and actively managing a diversified portfolio of debt securities, including bonds, loans and other asset-backed instruments.
Segment Information
Segment Reporting Disclosure [Text Block]
Number of LPs / LLCs with investment ownership percent over 25% (in businesses)
Number of LPs / LLCs with Equity Method Investment Ownership Percentage Over 25 percent
Number of LPs / LLCs with Equity Method Investment Ownership Percentage Over 25 percent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury obligations
U.S. Treasury obligations
U.S. Treasury obligations
US Treasury Securities [Member]
Reductions due to:
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Reductions [Abstract]
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Reductions
Other Commitments [Line Items]
Other Commitments [Line Items]
Increase (Decrease) in Stockholders' Equity:
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized Loss
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Workers' compensation
Workers' Compensation Alternative Market Business [Member]
Activity associated with our Alternative Market Business of our Workers' Compensation segment.
Transfers in
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3
Proceeds from sales or maturities of:
Proceeds from Sale, Maturity and Collection of Investments [Abstract]
Compensation Actually Paid vs. Total Shareholder Return
Compensation Actually Paid vs. Total Shareholder Return [Text Block]
Weighted Average
Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table]
Fair Value, Recurring and Nonrecurring [Table]
Deferred tax asset, net
Deferred Income Tax Assets, Net
Assets measured at fair value
Debt Securities, Available-for-Sale, Measurement Input
Schedule of Components of AOCI, Net of Tax
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Agency commercial mortgage-backed securities
Agency commercial mortgage-backed securities
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Accident Year [Domain]
Accident Year [Domain]
Accident Year [Domain]
Trading securities, cost
Debt Securities, Trading, Amortized Cost
Entity Central Index Key
Entity Central Index Key
PEO Name
PEO Name
Total revenues
Revenues
Foreign Currency Forwards
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net
Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year
Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other commercial mortgage-backed securities
Other Commercial Mortgage-Backed Securities [Member]
Other Commercial Mortgage-Backed Securities
Residential mortgage-backed securities
Residential mortgage-backed securities
Residential Mortgage-Backed Securities [Member]
Outstanding Aggregate Erroneous Compensation Amount
Outstanding Aggregate Erroneous Compensation Amount
Total
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims
Traditional business
Traditional Business [Member]
Traditional Business [Member]
Revolving Credit Facility
Revolving Credit Facility [Member]
Beginning balance
Ending balance
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value
Arrangement Duration
Trading Arrangement Duration
Schedule of Segment Reporting Information, by Segment [Table]
Schedule of Segment Reporting Information, by Segment [Table]
Securities on deposit with state insurance departments
Assets Held by Insurance Regulators
Premium receivable, allowance for credit loss
Premium Receivable, Allowance for Credit Loss
Segments [Axis]
Segments [Axis]
Corporate debt, multiple observable inputs
Corporate Bonds Multiple Observable Inputs [Member]
Debt securities that are issued by either a domestic or foreign corporate business entity with a promise of repayment and fair value has been determined using multiple observable inputs.
Exercise Price
Award Exercise Price
Entity Filer Category
Entity Filer Category
Local Phone Number
Local Phone Number
Financial
Equity Financial Securities [Member]
Equity securities in financial sector.
Additional 402(v) Disclosure
Additional 402(v) Disclosure [Text Block]
Investment ownership percentage
Investment In Unconsolidated Subsidiaries, Ownership Percentage
Investment In Unconsolidated Subsidiaries, Ownership Percentage
Other
Payment for (Proceeds from) Other Investing Activity
Assets
Assets [Abstract]
Credit Facility [Axis]
Credit Facility [Axis]
Contribution Certificates
Long-term Debt and Contribution Certificates, Fair Value Disclosure
Long-term Debt and Contribution Certificates, Fair Value Disclosure
Underlying Security Market Price Change
Underlying Security Market Price Change, Percent
Balance Sheet Location [Axis]
Statement of Financial Position Location, Balance [Axis]
Other Commitments [Axis]
Other Commitments [Axis]
Debt Instrument [Axis]
Debt Instrument [Axis]
Investment in unconsolidated subsidiaries
Investment in unconsolidated subsidiaries
Investment In Unconsolidated Subsidiaries
Investment In Unconsolidated Subsidiaries
Fair Value Measurement
Fair Value Disclosures [Text Block]
Credit Facility [Domain]
Credit Facility [Domain]
Shareholders' Equity
Equity, Attributable to Parent [Abstract]
Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year
Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member]
Total expenses
Benefits, Losses and Expenses
Entity Address, Address Line One
Entity Address, Address Line One
Expected gains reclassified
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net
Total gains (losses) realized and unrealized:
Gains Losses Realized and Unrealized Assets [Abstract]
Total gains (losses) realized and unrealized.
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent [Member]
Stated interest rate on debt
Debt Instrument, Interest Rate, Stated Percentage
Investment, Name [Axis]
Investment, Name [Axis]
Schedule of Gross Premiums by Product
Revenue from External Customers by Products and Services [Table Text Block]
Investments [Domain]
Investments [Domain]
Receivable from reinsurers on unpaid losses and loss adjustment expenses
Less reinsurance recoverables on unpaid losses and loss adjustment expenses
Plus reinsurance recoverables on unpaid losses and loss adjustment expenses
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments
Derivatives
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Other investments
Proceeds from Sale and Maturity of Other Investments
Portion of impairment losses recognized in other comprehensive income (loss) before taxes
Corporate debt
Impairment Losses, Investments, Portion In Other Comprehensive Loss, Before Tax, Portion Attributable To Parent
Impairment Losses, Investments, Portion In Other Comprehensive Loss, Before Tax, Portion Attributable To Parent
Other investments (at fair value, $2,546 and $2,077, respectively, otherwise at cost or amortized cost)
Other Long-Term Investments
Number of investment in any entity or affiliates greater than 10% of stockholders' equity
Number of Investment Affiliates Exceeding Shareholder's Equity Ten Percent Threshold Limit
Number of Investment Affiliates Exceeding Shareholder's Equity Ten Percent Threshold Limit
Net Investment Income
Net Investment Income [Abstract]
Other Liabilities
Other Liabilities [Member]
Depreciation and amortization, net of accretion
Depreciation and amortization, net of accretion
Depreciation, Amortization and Accretion, Net
Fair Value as of Grant Date
Award Grant Date Fair Value
Equity investments at fair value, cost
Equity Securities, FV-NI, Cost
Entity Registrant Name
Entity Registrant Name
Liquidating investments remaining period
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period
Stock Price or TSR Estimation Method
Stock Price or TSR Estimation Method [Text Block]
Deferred compensation liabilities
Deferred Compensation Liability, Current and Noncurrent
Other investments, measurement input
Alternative Investment, Measurement Input
Fair Value, Inputs, Level 1, 2 and 3
Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member]
Schedule of Outstanding Debt
Schedule of Long-Term Debt Instruments [Table Text Block]
Included in earnings, as a part of:
Gains Losses By Earnings Category Assets [Abstract]
Included in Earnings, as a part of.
Dilutive effect of securities (in shares)
Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements
Accordion feature borrowing capacity
Line of Credit Facility, Maximum Borrowing Capacity, Accordion Feature
Line of Credit Facility, Maximum Borrowing Capacity, Accordion Feature
Document Quarterly Report
Document Quarterly Report
Less than 12 months, Fair Value
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months
Number of limited partners to allow redemption by special consent
Number of Limited Partners to Allow Redemption by Special Consent
Number of Limited Partners to Allow Redemption by Special Consent
Total assets categorized within the fair value hierarchy
Assets, Fair Value Disclosure
Impairment losses
Total impairment losses:
Impairment Losses, Investments
Impairment Losses, Investments
Debt securities in unrealized loss position (in securities)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions
Schedule of Quantitative Information Regarding Level 3 Valuations
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]
Changed Peer Group, Footnote
Changed Peer Group, Footnote [Text Block]
Corporate debt, limited observable inputs
Corporate debt, limited observable inputs
Corporate Debt, Limited Observable Inputs [Member]
Corporate Debt, Limited Observable Inputs [Member]
Number of operating segments
Number of Operating Segments
Adjustment To PEO Compensation, Footnote
Adjustment To PEO Compensation, Footnote [Text Block]
Lloyd's Syndicates
Lloyd's Syndicates [Member]
Lloyd's Syndicates [Member]
Equity investments
Payments to Acquire Equity Securities, FV-NI
Schedule of Investments in LLCs and Limited Partnerships
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block]
Investment Type [Axis]
Schedule of Investment Income, Reported Amounts, by Category [Axis]
Investment Type [Axis]
Segment reconciling items
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member]
Total Investments
Investments
Title
Trading Arrangement, Individual Title
Peer Group Total Shareholder Return Amount
Peer Group Total Shareholder Return Amount
Operating expense
Other Underwriting Expense
BOLI
Investment Income (Loss), Bank Owned Life Insurance
Investment Income (Loss), Bank Owned Life Insurance
Restatement Determination Date:
Restatement Determination Date [Axis]
Number of limited partners, redemption allowed with prior notice
Number of Limited Partners, Redemption Allowed with Prior Notice
Number of Limited Partners, Redemption Allowed with Prior Notice
Net effect of restricted and performance shares issued
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture
Non-PEO NEO
Non-PEO NEO [Member]
Allowance for expected credit losses
Allowance for Expected Credit Losses
Allowance for credit loss beginning balance
Allowance for credit loss ending balance
Debt Securities, Available-for-Sale, Allowance for Credit Loss
Accumulated Other Comprehensive Income (Loss) [Table]
Accumulated Other Comprehensive Income (Loss) [Table]
Schedule of Interest Rate Swaps
Schedule of Interest Rate Derivatives [Table Text Block]
Provision for income taxes:
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Other
Proceeds from (Payment for) Other Financing Activity
Net sales or maturities (purchases) of short-term investments
Payments for (Proceeds from) Short-Term Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Threshold limit of investments based on shareholders' equity
Threshold Limit Of Investments Based On Shareholders Equity
Threshold Limit Of Investments Based On Shareholders Equity
Gross Unrealized Gains
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax
Name
Trading Arrangement, Individual Name
Award Type [Domain]
Award Type [Domain]
Net favorable prior year reserve development
Net Favorable Prior Year Reserve Development
Net Favorable Prior Year Reserve Development
Common shares issued for compensation
Stock Issued During Period, Value, Other
Equity Awards Adjustments
Equity Awards Adjustments [Member]
Other, net
Other Noncash Income (Expense)
Pension Benefits Adjustments, Footnote
Pension Benefits Adjustments, Footnote [Text Block]
Other income (expense)
Other income (expense)
Other Income
Compensation Amount
Outstanding Recovery Compensation Amount
Debt Instrument, Name [Domain]
Debt Instrument, Name [Domain]
Schedule of Reserve for Losses and Loss Adjustment Expenses
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]
Statement of Comprehensive Income [Abstract]
Statement of Comprehensive Income [Abstract]
Recovery of Erroneously Awarded Compensation Disclosure [Line Items]
Fair Value
Estimate of Fair Value Measurement [Member]
MNPI Disclosure Timed for Compensation Value
MNPI Disclosure Timed for Compensation Value [Flag]
Name
Awards Close in Time to MNPI Disclosures, Individual Name
Other net investment gains (losses)
Other Net Realized Investment Gain (Loss)
Other net realized investment gains (losses).
Increase (decrease) in fair value of contingent consideration issued in NORCAL acquisition
Contingent Consideration
Business Combination, Contingent Consideration, Change in Contingent Consideration, Liability, Increase (Decrease)
Weighted average number of common shares outstanding:
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Aggregate Erroneous Compensation Not Yet Determined
Aggregate Erroneous Compensation Not Yet Determined [Text Block]
Commitments total
Other Commitment
All other
All Other [Member]
Equity securities in industry sectors that are not listed separately.
Qualified affordable housing project tax credit partnerships
Qualified Affordable Housing Tax Credit Partnerships [Member]
Qualified Affordable Housing Tax Credit Partnerships [Member]
Revenues
Revenues [Abstract]
Other investments
Fair Value
Alternative Investment
Required FAL deposit
Deposit Assets
Share-based compensation
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition
Investment redemption notice period
Fair Value, Investments, Entities that Calculate Net Asset Value, Investment Redemption, Notice Period, One Fund
Fair Value, Investments, Entities that Calculate Net Asset Value, Investment Redemption, Notice Period, One Fund
Private debt funds
Private Debt Funds [Member]
Private Debt Funds [Member]
Accumulated other comprehensive income (loss) (net of deferred tax expense (benefit) of ($31,587) and ($46,681), respectively)
Accumulated Other Comprehensive Income (Loss), Net of Tax
Bond funds
Fixed Income Funds [Member]
Financial Instruments [Domain]
Financial Instruments [Domain]
Gain on sale of intangible assets
Gain (Loss) on Disposition of Intangible Assets
Segments [Domain]
Segments [Domain]
Purchases
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases
Income Statement Location [Axis]
Statement of Income Location, Balance [Axis]
Performance Share Units
Performance Shares [Member]
Investments
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]
Aggregate Pension Adjustments Service Cost
Aggregate Pension Adjustments Service Cost [Member]
Included in other comprehensive income (loss)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)
Fair Value, Measurements, Fair Value Hierarchy [Domain]
Fair Value Hierarchy and NAV [Domain]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net Investment Income [Line Items]
Number of limited partners in investment
Number of Limited Partners In Investment
Number of Limited Partners In Investment
Qualifying Cash Flow Hedges - Gains (Losses) Reclassified from AOCI, net of tax, to Earnings
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax
Balance Sheet Location [Domain]
Statement of Financial Position Location, Balance [Domain]
Minimum
Minimum
Minimum [Member]
Company Selected Measure Name
Company Selected Measure Name
Premiums receivable
Increase (Decrease) in Premiums Receivable
Fair Value Measurement [Domain]
Fair Value Measurement [Domain]
Other investments, portion carried at fair value
Other Investments, Fair Value Disclosure
Other Investments, Fair Value Disclosure
Fixed maturities, available-for-sale
Purchases
Payments to Acquire Debt Securities, Available-for-Sale
Aggregate Available
Trading Arrangement, Securities Aggregate Available Amount
State and municipal bonds
State and municipal bonds
US States and Political Subdivisions Debt Securities [Member]
Stock Appreciation Rights (SARs)
Stock Appreciation Rights (SARs) [Member]
Pre-tax transaction related costs
Pre-tax transaction related costs
Business Combination, Acquisition Related Costs, Before Tax
Business Combination, Acquisition Related Costs, Before Tax
All Executive Categories
All Executive Categories [Member]
Net losses and loss adjustment expenses
Current year
Current Year Claims and Claims Adjustment Expense
DPAC amortization
Deferred Policy Acquisition Costs, Amortization Expense
Common shares (par value $0.01 per share, 100,000,000 shares authorized, 64,020,611 and 63,763,789 shares issued, respectively)
Common Stock, Value, Issued
Fair value
Investments continuous unrealized loss position [Abstract]
Investments Continuous Unrealized Loss Position.
Tax Period [Axis]
Tax Period [Axis]
Liability for Claims and Claims Adjustment Expense [Table]
Liability for Claims and Claims Adjustment Expense [Table]
Net premiums earned
Net premiums earned
Segment net premiums earned
Premiums Earned, Net
Commitments and Contingencies
Commitments and Contingencies Disclosure [Text Block]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]
Diluted (in shares)
Weighted average number of common shares outstanding, diluted (in shares)
Weighted Average Number of Shares Outstanding, Diluted
Non-GAAP Measure Description
Non-GAAP Measure Description [Text Block]
Derivative [Table]
Derivative [Table]
Losses (gains) recorded
Investment Program, Proportional Amortization Method, Elected, Equity Method Investment, Income (Loss) from Tax Credit Investment
Fair Value Measured at Net Asset Value Per Share
Fair Value Measured at Net Asset Value Per Share [Member]
Business Combination [Axis]
Business Combination [Axis]
Entity Small Business
Entity Small Business
Impairment has been previously recognized
Impairment Loss, Debt Securities, Impairment Previously Recognized
Impairment Loss, Debt Securities, Impairment Previously Recognized
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Abstract]
Equity investments
Proceeds from Sale and Maturity, Debt Security, Trading, and Equity Security, FV-NI, Held-for-Investment
Workers' Compensation Insurance
Workers' Compensation Insurance Segment
Workers' Compensation Insurance Segment [Member]
Workers' Compensation Insurance Segment
Debt
Long-Term Debt [Text Block]
Document Transition Report
Document Transition Report
Schedule of Net Investment Income
Investment Income [Table Text Block]
Short-term investments
Short-Term Investments [Member]
SPC U.S. federal income tax expense (benefit)
SPC U.S. federal income tax benefit (expense)
Segregated Portfolio Cells Income Tax Expense (Benefit)
Segregated Portfolio Cells Income Tax Expense (Benefit)
Underlying Securities
Award Underlying Securities Amount
Gross realized gains, available-for-sale fixed maturities
Debt Securities, Available-for-Sale, Realized Gain
Short-term investments, including Other
Short-Term Investments and Other Invested Assets [Member]
Short-term investments and Other invested assets [Member]
Equity Component [Domain]
Equity Component [Domain]
Document Period End Date
Document Period End Date
PEO Actually Paid Compensation Amount
PEO Actually Paid Compensation Amount
Income Taxes
Income Tax Disclosure [Text Block]
Awards Close in Time to MNPI Disclosures, Table
Awards Close in Time to MNPI Disclosures [Table Text Block]
Total authorizations which remain available for use
Stock Repurchase Or Debt Repayment Remaining Authorized Amount
The remaining amount authorized by an entity's Board of Directors for stock repurchase or debt repayment.
Discounted Cash Flows
Valuation, Income Approach [Member]
Accident Year [Axis]
Accident Year [Axis]
Accident Year
Revolving Credit Agreement and Term Loan
Debt Instrument, Fair Value Disclosure
Scenario [Axis]
Scenario [Axis]
Unsettled security transactions, net change
Unsettled security transactions net
Unsettled security transactions, net.
Surplus notes
Surplus Notes
Second greatest unrealized loss position
Second Greatest Unrealized Loss Position
Second greatest unrealized loss position.
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Claims and Claims Adjustment Expense [Line Items]
Document Type
Document Type
Level 3
Fair Value, Inputs, Level 3 [Member]
Earnings (Loss) Per Share
Earnings Per Share [Text Block]
Reserve for Losses and Loss Adjustment Expenses
Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]
Name
Outstanding Recovery, Individual Name
Product and Service [Axis]
Product and Service [Axis]
Derivative Contract [Domain]
Derivative Contract [Domain]
Business owned life insurance
Life Insurance, Corporate or Bank Owned, Amount
Gross realized (losses), available-for-sale fixed maturities
Debt Securities, Available-for-Sale, Realized Loss
All Individuals
All Individuals [Member]
Line of credit, borrowing capacity including accordion feature
Line Of Credit Facility, Maximum Borrowing Capacity, Including Accordion Feature
Line Of Credit Facility, Maximum Borrowing Capacity, Including Accordion Feature
Long-term Debt, Type [Domain]
Long-Term Debt, Type [Domain]
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Abstract]
Name
Forgone Recovery, Individual Name
Accident Year 2018 through 2022
Accident Year 2018 through 2022 [Member]
Accident Year 2018 through 2022
Schedule of Investment Income, Reported Amounts, by Category [Table]
Investment Income [Table]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Debt Securities, Available-for-Sale, Allowance for Credit Loss [Line Items]
Statistical Measurement [Axis]
Statistical Measurement [Axis]
Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested
Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member]
Gain on fair value of contingent consideration
Business Combination, Contingent Consideration, Change in Contingent Consideration, Asset, Increase (Decrease)
Net sales or (purchases) of fixed maturities, trading
Proceeds from (Payments for) Trading Securities, Short-Term
Derivative, fixed interest rate
Derivative, Fixed Interest Rate
Net investment gains (losses)
Gain (Loss) on Investments [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Aggregate Erroneous Compensation Amount
Aggregate Erroneous Compensation Amount
Peer Group Issuers, Footnote
Peer Group Issuers, Footnote [Text Block]
Due after one year through five years
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value
Short-term investments
Other Short-Term Investments
Gain on sale of capital assets
Gain (Loss) on Sale of Properties
Erroneous Compensation Analysis
Erroneous Compensation Analysis [Text Block]
Other
Gain (Loss) on Sale of Other Investments
Other comprehensive income (loss), after tax, net of reclassification adjustments
Net OCI, current period
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Deferred tax expense (benefit) on accumulated other comprehensive income (loss)
AOCI Tax, Attributable to Parent
Equity in earnings (loss) of unconsolidated subsidiaries
Equity in (earnings) loss of unconsolidated subsidiaries
Equity in earnings (loss) of unconsolidated subsidiaries
Equity In Earnings (Loss) Of Unconsolidated Subsidiaries
Equity In Earnings (Loss) Of Unconsolidated Subsidiaries
NORCAL Group
NORCAL Group [Member]
NORCAL Group [Member]
Other liabilities
Other Liabilities, Fair Value Disclosure
Schedule of Derivative Instruments, Gain (Loss)
Derivative Instruments, Gain (Loss) [Table Text Block]
Rule 10b5-1 Arrangement Terminated
Rule 10b5-1 Arrangement Terminated [Flag]
Level 1
Fair Value, Inputs, Level 1 [Member]
Gain on disposition of assets
Gain (Loss) on Disposition of Assets
Diluted (in usd per share)
Earnings Per Share, Diluted
Forecast
Forecast [Member]
Erroneously Awarded Compensation Recovery
Erroneously Awarded Compensation Recovery [Table]
Title of 12(b) Security
Title of 12(b) Security
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Expense
Other Expense [Member]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]
Accident Year 2022 and 2023
Accident Year 2022 and 2023 [Member]
Accident Year 2022 and 2023
Single greatest unrealized loss position
Single Greatest Unrealized Loss Position
Single greatest unrealized loss position.
Treasury shares (in shares)
Treasury Stock, Common, Shares
Earnings (loss) per share:
Earnings Per Share [Abstract]
Earnings Per Share [Abstract]
Paid related to:
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Consolidation Items [Domain]
Consolidation Items [Domain]
Debt securities in unrealized loss position as percentage of total debt securities held
Number Of Debt Securities In Unrealized Loss Position As Percentage Of Debt Securities
Number of debt securities in unrealized loss position as percentage of total debt securities.
Return of invested capital from unconsolidated subsidiaries
Proceeds from Equity Method Investment, Distribution, Return of Capital
Total Policy Liabilities and Accruals
Policy Liabilities
Total policy liabilities.
Investments, Debt and Equity Securities [Abstract]
Investments, Debt and Equity Securities [Abstract]
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity, Not Primary Beneficiary [Member]
Other asset-backed securities
Other asset-backed securities
Asset-Backed Securities, Securitized Loans and Receivables [Member]
No allowance for credit losses has been previously recognized
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Not Previously Recorded
Tax credit carryforwards
Tax Credit Carryforward, Amount
Portfolio Cell Reinsurance
Portfolio Cell Reinsurance [Member]
Portfolio Cell Reinsurance
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Award Timing Disclosures [Line Items]
Total principal
Long-Term Debt, Gross
Schedule of Net Realized Investment Gains (Losses)
Gain (Loss) on Securities [Table Text Block]
Measurement Frequency [Domain]
Measurement Frequency [Domain]
Net balance, beginning of year
Net balance, end of period
Liability for Unpaid Claims and Claims Adjustment Expense, Net
Unfunded Contractual Commitments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments
Shareholders' Equity
Equity [Text Block]
Due after five years through ten years
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value
Net income (loss)
Net income (loss)
Net Income (Loss) Attributable to Parent
Inter-segment Eliminations
Intersegment Eliminations [Member]
Schedule of Investments Held in an Unrealized Loss Position
Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block]
Expiration Date
Trading Arrangement Expiration Date
Other Commitments [Domain]
Other Commitments [Domain]
Interest rate swaps
Interest Rate Cash Flow Hedge Liability at Fair Value
Issuers in unrealized loss position (in issuers)
Available For Sale Securities In Unrealized Loss Positions Number Of Issuers
Available For Sale Securities In Unrealized Loss Positions.
Other liabilities
Increase (Decrease) in Other Operating Liabilities
Product Information [Line Items]
Product Information [Line Items]
Change in unrealized holding gains (losses), equity investments
Equity Securities, FV-NI, Unrealized Gain (Loss)
Balance beginning of period
Balance ending of period
Credit Losses Recognized In Earnings In Which A Portion Of Losses Are Recognized In Comprehensive Income (Loss), Credit Losses On Debt Securities Held
Credit Losses Recognized In Earnings In Which A Portion Of Losses Are Recognized In Comprehensive Income (Loss), Credit Losses On Debt Securities Held
Other investments
Other Investments
Other investments
Other Investments [Member]
Schedule of Equity Method Investments
Equity Method Investments [Table Text Block]
Real estate, net
Property, Plant and Equipment, Net
Segment Reporting Information [Line Items]
Segment Reporting Information [Line Items]
Preferred stock, shares authorized (in shares)
Preferred Stock, Shares Authorized
Long/short equity funds
Long/Short Equity Funds [Member]
Long/Short Equity Funds [Member]
Income taxes payable
Taxes Payable
Adoption Date
Trading Arrangement Adoption Date
Reclassifications
Reclassification, Comparability Adjustment [Policy Text Block]
Compensation Actually Paid vs. Net Income
Compensation Actually Paid vs. Net Income [Text Block]
Contribution Certificates
Contribution Certificate due 2031 [Member]
Contribution Certificate due 2031
Entity Current Reporting Status
Entity Current Reporting Status
Funding Commitments
Funding Commitments [Member]
Funding Commitments [Member]
Derivative [Line Items]
Derivative [Line Items]
Awards Close in Time to MNPI Disclosures
Awards Close in Time to MNPI Disclosures [Table]
Consolidated Entities [Domain]
Consolidated Entities [Domain]
Line of Credit
Line of Credit [Member]
Retained earnings
Retained Earnings (Accumulated Deficit)
Corporate
Corporate Segment [Member]
Financial Instrument [Axis]
Financial Instrument [Axis]
Alternative market business
Alternative Market Business [Member]
Alternative Market Business [Member]
Statement of Financial Position [Abstract]
Statement of Financial Position [Abstract]
Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested
Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member]
Executive Category:
Executive Category [Axis]
Foreign Currency Forwards
Foreign Exchange Forward [Member]
12 months or longer, Unrealized Loss
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss
(Increase) decrease in cash surrender value of BOLI
Life Insurance, Corporate or Bank Owned, Change in Value
Market Comparable Securities
Valuation, Market Approach [Member]
Current Fiscal Year End Date
Current Fiscal Year End Date
Cash Flow Hedging Gains (Losses)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Less than 12 months, Unrealized Loss
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss
Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table
Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member]
Credit Derivatives [Line Items]
Credit Derivatives [Line Items]
Prior years
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years
Net investment gains (losses):
Realized Investment Gains (Losses) [Abstract]
Statement [Table]
Statement [Table]
Number of employees
Workers Compensation Insurance Products, Maximum Employees Per Company
Workers Compensation Insurance Products, Maximum Employees Per Company
Securities sold during the period
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Sell before Recovery
Investment in unconsolidated subsidiaries
Payments For (Proceeds From) Investment In Unconsolidated Subsidiaries
The cash outflow associated with an entity's investment in equity method investments.
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]
Deferred expense (benefit)
Deferred income tax expense (benefit)
Deferred Income Tax Expense (Benefit)
Financing Activities
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Equity Awards Adjustments, Excluding Value Reported in Compensation Table
Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member]
Non government-backed
Non Government-Backed [Member]
Securities that are not backed by the U.S. government or U.S. government agencies.
Unrealized Loss
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss
Schedule of Fair Value of Assets
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
Other comprehensive (income) loss, reclassification adjustment from AOCI for write-down of securities, before tax
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax
Equity investments, at fair value (cost, $120,602 and $145,411, respectively)
Equity investments
Equity Securities, FV-NI, Current
Basis of Presentation
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]
Antidilutive shares excluded from computation of earnings per share (in shares)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount
Schedule of Fair Value Measurements - Level 3 Assets & Liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
All Adjustments to Compensation
All Adjustments to Compensation [Member]
Fair Value, by Balance Sheet Grouping [Table]
Fair Value, by Balance Sheet Grouping [Table]
Amendment Flag
Amendment Flag
Sales
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales
Reserve for losses and loss adjustment expenses
Balance, beginning of year
Balance, end of period
Liability for Claims and Claims Adjustment Expense
Net investment (gains) losses
Net investment gains (losses)
Gain (Loss) on Sale of Investments, Excluding Sale of Properties
Gain (Loss) on Sale of Investments, Excluding Sale of Properties
Treasury shares, at cost (12,606,968 shares as of each respective period end)
Treasury Stock, Common, Value
PPM RRG
PPM RRG [Member]
PPM RRG
Other Commitments [Table]
Other Commitments [Table]
An allowance for credit losses was recorded in a previous period
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)
Termination Date
Trading Arrangement Termination Date
Net cash provided (used) by financing activities
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation
Insider Trading Policies and Procedures Adopted
Insider Trading Policies and Procedures Adopted [Flag]
Measure:
Measure [Axis]
Number of instruments (in derivative instruments)
Number of Interest Rate Derivatives Held
Foreign currency exchange rate (gains) losses
Realized Gain (Loss), Foreign Currency Transaction, before Tax
Valuation Approach and Technique [Axis]
Valuation Approach and Technique [Axis]
MPL
MPL [Member]
MPL
Basic (in shares)
Weighted average number of common shares outstanding, basic (in shares)
Weighted Average Number of Shares Outstanding, Basic
Other asset-backed securities
Other Asset-Backed Securities [Member]
Other Asset-Backed Securities [Member]
Schedule of Earnings Per Share, Basic and Diluted
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Income tax benefit (expense)
Income Tax Expense (Benefit), Excluding Business Acquisition Tax Effect
Income Tax Expense (Benefit), Excluding Business Acquisition Tax Effect
Segment Reporting [Abstract]
Segment Reporting [Abstract]
Minimum period for claims resolution
Minimum Period For Claims Resolution
Minimum Period For Claims Resolution
Pay vs Performance Disclosure, Table
Pay vs Performance [Table Text Block]
Due after ten years
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value
Debt Disclosure [Abstract]
Debt Disclosure [Abstract]
Forgone Recovery due to Violation of Home Country Law, Amount
Forgone Recovery due to Violation of Home Country Law, Amount
Investment fees and expenses
Investment Income, Investment Expense
Entity Tax Identification Number
Entity Tax Identification Number
Scenario [Domain]
Scenario [Domain]
Other
Other Premiums [Member]
Other Premiums [Member]
Net realized gains (losses), trading fixed maturities
Debt Securities, Trading, Realized Gain (Loss)
Strategy focused funds
Strategy Focused Fund [Member]
Strategy Focused Fund [Member]
Forgone Recovery due to Expense of Enforcement, Amount
Forgone Recovery due to Expense of Enforcement, Amount
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Consolidated Entities [Axis]
Consolidated Entities [Axis]
Common shares, par value (in usd per share)
Common Stock, Par or Stated Value Per Share
Common shares, shares issued (in shares)
Common Stock, Shares, Issued
Derivative Asset, Statement of Financial Position [Extensible Enumeration]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]
Other commercial mortgage-backed securities
Other commercial mortgage-backed securities
Commercial Mortgage-Backed Securities [Member]
Net realized gains (losses), equity investments
Equity Securities, FV-NI, Realized Gain (Loss)
Accounting Policies
Use of Estimates, Policy [Policy Text Block]
Number of proassurance's insurance subsidiaries
Number of Insurance Subsidiaries
Number of Insurance Subsidiaries
Deferred tax (benefit) expense included in OCI
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table]
Trading Arrangement:
Trading Arrangement [Axis]
Total Shareholder Return Amount
Total Shareholder Return Amount
Net investment gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings
Change in unrealized holding gains (losses), convertible securities, carried at fair value
Unrealized Gain (Loss) on Hybrid Instrument, Net
Insider Trading Arrangements [Line Items]
Security Exchange Name
Security Exchange Name
Equity investments
Equity Investments
Equities
Equity Securities [Member]
Total Liabilities
Liabilities
Liabilities
Residential mortgage-backed, other commercial mortgage-backed and other asset-backed securities
Collateralized Mortgage-Backed Securities [Member]
Capital contribution received from (return of capital to) external segregated portfolio cell participants
External Capital Contribution Received (Return Of Capital) For Segregated Portfolio Cells
External Capital Contribution Received (Return Of Capital) For Segregated Portfolio Cells
Ceded premiums earned
Ceded Premiums Earned
Pension Adjustments Prior Service Cost
Pension Adjustments Prior Service Cost [Member]
Fixed maturities, available-for-sale
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale
Expenses
Operating Expenses [Abstract]
Material Terms of Trading Arrangement
Material Terms of Trading Arrangement [Text Block]
Segregated Portfolio Cell Reinsurance
Segregated Portfolio Cell Reinsurance Segment
Segregated Portfolio Cell Reinsurance [Member]
Segregated Portfolio Cell Reinsurance [Member]
Included in earnings
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings
Summary of reserve for losses and loss adjustment expenses
Liability for Claims and Claims Adjustment Expense [Roll Forward]
Liability for Claims and Claims Adjustment Expense
Proceeds from sale of capital assets
Proceeds from Sale of Other Productive Assets
Statement [Line Items]
Statement [Line Items]
Asset-backed Securities
Asset-backed securities
Asset-Backed Securities [Member]
Less unamortized debt issuance costs
Unamortized Debt Issuance Expense
Consolidation Items [Axis]
Consolidation Items [Axis]
Rule 10b5-1 Arrangement Adopted
Rule 10b5-1 Arrangement Adopted [Flag]
Cash and cash equivalents
Cash and Cash Equivalent
Specialty P&C
Specialty P&C
Specialty P&C Segment
Specialty Property and Casualty [Member]
Specialty Property and Casualty [Member]
Fair Value Measurement Inputs and Valuation Techniques [Table]
Fair Value Measurement Inputs and Valuation Techniques [Table]
Revolving Credit Agreement
Revolving Credit Agreement [Member]
Revolving Credit Agreement
Common Stock
Common Stock [Member]
Fixed maturities, available-for-sale, at fair value (amortized cost, $3,810,930 and $3,803,835, respectively; allowance for expected credit losses, $2,774 and $3,399, respectively)
Fixed maturities, available-for-sale
Estimated Fair Value
Total Fair Value
Debt Securities, Available-for-Sale
Entity Incorporation, State or Country Code
Entity Incorporation, State or Country Code
Non-NEOs
Non-NEOs [Member]
Corporate Debt
Corporate debt
Corporate Debt Securities [Member]
Gross premiums earned:
Gross Premiums Earned
Amount of premiums earned before premiums ceded to other entities, including directed and assumed premiums earned.
Increase (decrease) in cash and cash equivalents
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation