EBP WRPSP EBP WRPSP [Member] EBP WRPSP Rollovers EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Maximum Maximum [Member] Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] EBP, Description of Plan [Table] EBP, Description of Plan [Table] Mutual Funds Mutual Fund [Member] Total Fully Corrected Under VFCP and PTE EBP, Schedule of Delinquent Participant Contribution, Corrected Other Investments EBP, Other Investment [Member] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Pretax, maximum annual compensation to total compensation, percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Fully Benefit-Responsive Investment Contract [Table] EBP, Fully Benefit-Responsive Investment Contract [Table] Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Maximum borrowing, amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Fair Value Measurements of Investments EBP, Investment, Fair Value and NAV [Text Block] Minimum borrowing, amount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Payable for trustee, administrative fees and other EBP, Accrued Expense EBP, Fully Benefit-Responsive Investment Contract [Abstract] Total Investments, at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Money Market Fund Money Market Funds [Member] Fair Value, Inputs, Level 1 Fair Value, Inputs, Level 1 [Member] Investment in Stable Value Fund EBP, Fully Benefit-Responsive Investment Contract [Text Block] EBP, Investment, Fair Value and NAV [Abstract] Total Assets EBP, Asset Assets: EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Additions to net assets attributed to: EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Payment of Benefits EBP, Payment to Participant [Policy Text Block] Total Liabilities EBP, Liability After-tax, maximum annual compensation to total compensation, percentage EBP, Participant Contribution, After-Tax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Participant Contribution, After-Tax, Maximum Annual Compensation to Total Compensation, Percentage Amendment Flag Amendment Flag Nonvested terminated participants, forfeited amounts during period EBP, Nonvested Terminated Participants, Forfeited Amounts During Period EBP, Nonvested Terminated Participants, Forfeited Amounts During Period Basis of Accounting EBP, Basis of Accounting [Policy Text Block] EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] Investment, number of shares (in shares) EBP, Investment, Number of Shares EBP, Description of Plan and Accounting Change [Abstract] Schedule of Plan Assets at Fair Value EBP, Investment, Fair Value and NAV [Table Text Block] Primary residence, borrowing term EBP, Note Receivable From Participant, Account, Primary Residence, Maximum Borrowing Term EBP, Note Receivable From Participant, Account, Primary Residence, Maximum Borrowing Term EBP, Schedule of Delinquent Participant Contribution [Abstract] Investments [Domain] Investments [Domain] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] Use of Estimate EBP, Use of Estimate [Policy Text Block] Schedule H, Line 4i – Schedule of Assets (Held at End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] EBP, Employer Profit Sharing Contribution, Tax-Deferred, Fully Vested EBP, Employer Profit Sharing Contribution, Tax-Deferred, Fully Vested [Member] EBP, Employer Profit Sharing Contribution, Tax-Deferred, Fully Vested Risks and Uncertainties EBP, Risk and Uncertainty [Text Block] Employer EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash EBP, Schedule of Delinquent Participant Contribution [Line Items] EBP, Schedule of Delinquent Participant Contribution [Line Items] Minimum Minimum [Member] Interest on participant loans EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Investment Type [Axis] Investment Type [Axis] Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Participants EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Interest and dividends EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Plan Description EBP, Description of Plan [Text Block] Pending Correction in VFCP EBP, Schedule of Delinquent Participant Contribution, Pending Correction in VFCP Vesting percentage EBP, Employer Contribution, Vesting Percentage EBP, Employer Contribution, Vesting Percentage EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] Minimum percentage of participant earnings EBP, Employer Contribution, Minimum Amount, Percentage of Participant Earnings EBP, Employer Contribution, Minimum Amount, Percentage of Participant Earnings EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] Total additions EBP, Change in Net Asset Available for Benefit, Increase Eligible earnings, first year of employment, minimum hours of service EBP, Eligible Earnings, First Year of Employment, Minimum Hours of Service EBP, Eligible Earnings, First Year of Employment, Minimum Hours of Service Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Termination of benefits, maximum installment period EBP, Termination of Benefits, Maximum Installment Period EBP, Termination of Benefits, Maximum Installment Period Investment, Identifier [Axis] Investment, Identifier [Axis] Total investments and participant loans EBP, Asset Held for Investment General loan, borrowing term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term Document Information [Line Items] Document Information [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Line Items] Requisite service period EBP, Requisite Service Period EBP, Requisite Service Period EBP, Risk and Uncertainty [Table] EBP, Risk and Uncertainty [Table] EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Fair Value, Inputs, Level 2 Fair Value, Inputs, Level 2 [Member] Forfeited accounts, first year of employment, minimum hours of service EBP, Eligible Earnings, Forfeited Accounts, First Year of Employment, Minimum Hours of Service EBP, Eligible Earnings, Forfeited Accounts, First Year of Employment, Minimum Hours of Service EBP, Fully Benefit-Responsive Investment Contract [Line Items] EBP, Fully Benefit-Responsive Investment Contract [Line Items] Corrected Outside VFCP EBP, Schedule of Delinquent Participant Contribution, Corrected Outside VFCP EBP, Tax Status [Table] EBP, Tax Status [Table] Net increase in net assets available for plan benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Related Party Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Contributions receivable employer EBP, Employer Contribution, Receivable Automatic deferral rate EBP, Participant Contribution, Automatic, Deferral Rate Investments, at fair value (note 6): EBP, Investment, Fair Value [Abstract] Lost interest EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan, Lost Interest EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan, Lost Interest Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Investment, current value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Transferred Late to Plan EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Eligible earnings, minimum hours of service EBP, Eligible Earnings, First Calendar Quarter, Minimum Hours of Service EBP, Eligible Earnings, First Calendar Quarter, Minimum Hours of Service Other expenses, net EBP, Change in Net Asset Available for Benefit, Decrease from Other Expenses, Net EBP, Change in Net Asset Available for Benefit, Decrease from Other Expenses, Net EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] Payable for securities purchased EBP, Liability for Investment Purchase EBP, Tax Status [Abstract] W. R. Berkley Corporation Common Stock Fund EBP, Employer, Common Stock Fund [Member] Number of participant loans outstanding EBP, Note Receivable from Participant, Account, Number of Loans Outstanding EBP, Note Receivable from Participant, Account, Number of Loans Outstanding Cash EBP, Noninterest-Bearing Cash Participant loan, current value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Investment Valuation and Income Recognition, Cash and Cash Equivalents EBP, Investment [Policy Text Block] Fair Value, Inputs, Level 1, Level 2, and Level 3 Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Participant loan, term EBP, Asset Held for Investment, Participant Loan, Maturity Period EBP, Asset Held for Investment, Participant Loan, Maturity Period Plan Termination EBP, Plan Termination [Text Block] EBP, Employer Profit Sharing Contribution, Subject to Vesting Schedule EBP, Employer Profit Sharing Contribution, Subject to Vesting Schedule [Member] EBP, Employer Profit Sharing Contribution, Subject to Vesting Schedule Entity Central Index Key Entity Central Index Key Participant loan, interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Automatic deferral rate, annual increase EBP, Participant Contribution, Automatic, Annual Increase Deferral Rate EBP, Participant Contribution, Automatic, Annual Increase Deferral Rate Common Collective Trusts Common Collective Trust [Member] EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] EBP, Risk and Uncertainty [Abstract] EBP, Subsequent Event [Table] EBP, Subsequent Event [Table] Deductions from net assets attributed to: EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Participant loans receivable EBP, Note Receivable from Participant Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Entity Registrant Name Entity Registrant Name Concentration of investment to net assets, percentage EBP, Risk and Uncertainty, Concentration of Investment at Fair Value to Net Assets, Percentage EBP, Subsequent Event [Abstract] EBP, Liability [Abstract] EBP, Liability [Abstract] Subsequent Events EBP, Subsequent Event [Text Block] Schedule H, Line 4a - Schedule of Delinquent Participant Contributions EBP, Schedule of Delinquent Participant Contribution [Text Block] EBP, Schedule of Delinquent Participant Contribution [Table] EBP, Schedule of Delinquent Participant Contribution [Table] Tax Status EBP, Tax Status [Text Block] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type Contribution to eligible compensation, percentage EBP, Participant Contribution, Contribution to Eligible Compensation, Percentage EBP, Participant Contribution, Contribution to Eligible Compensation, Percentage Maximum borrowing, to total account, percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Line Items] Document Information [Table] Document Information [Table] EBP, Employer Profit Sharing Contribution EBP, Employer Profit Sharing Contribution [Member] EBP, Employer Profit Sharing Contribution Net investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Submission delay (in days) EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan, Period EBP, Schedule of Delinquent Participant Contribution, Transferred Late to Plan, Period Allocation percentage EBP, Employer Contribution, Allocation Percentage EBP, Employer Contribution, Allocation Percentage EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Not Corrected EBP, Schedule of Delinquent Participant Contribution, Not Corrected Net assets available for plan benefits Net assets available for benefits at beginning of year Net assets available for benefits at end of year EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions: EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Forfeited nonvested account EBP, Forfeited Nonvested Account Maximum number loans held by participant EBP, Asset Held for Investment, Participant Loan, Maximum Number Outstanding EBP, Asset Held for Investment, Participant Loan, Maximum Number Outstanding Mandatory distribution, terminated participant minimum vested account balance EBP, Involuntary Cash-out Limit EBP, Involuntary Cash-out Limit Fixed Income Investments Fixed Income Investments [Member] Fair Value Measured at Net Asset Value Per Share Fair Value Measured at Net Asset Value Per Share [Member] EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items] Eligible earnings, consecutive month period from first hour of service EBP, Eligible Earnings, Consecutive Month Period from First Hour of Service EBP, Eligible Earnings, Consecutive Month Period from First Hour of Service