XML 83 R73.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Reserves for Loss and Loss Expenses (Narrative) (Details) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Mar. 31, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Net of loss reserves discount | $ 22,000,000 |  | $ 26,000,000 | $ 22,000,000
Increase (decrease) in estimates for claims |  |  | 7,000,000 | (6,000,000)
Adjustment expense |  | $ 24,000,000 | 2,000,000 | 21,000,000
Liability recognized for best estimate net of reinsurance |  |  | 388,000,000 |
Liability recognized for best estimate net of reinsurance, reported losses |  |  | 385,000,000 |
Liability recognized for best estimate net of reinsurance, incurred but not reported (IBNR) |  |  | 3,000,000 |
Insurance |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Liability recognized for best estimate net of reinsurance |  |  | 329,000,000 |
Unfavorable reserve development net of premium offsets |  |  | 5,000,000 | 19,000,000
Reinsurance & Monoline Excess |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Liability recognized for best estimate net of reinsurance |  |  | 59,000,000 |
Unfavorable reserve development net of premium offsets |  |  |  | $ 2,000,000
Favorable reserve development net of premium offsets | $ 3,000,000 |  | $ 7,000,000 |

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpenseLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
Name: | us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Favorable Reserve Development Net Of Premium Offsets + References No definition available. + Details
Name: | wrb_FavorableReserveDevelopmentNetOfPremiumOffsets
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Liability for Claims and Claims Adjustment Expense, Net Of Reinsurance, Incurred but Not Reported (IBNR) Claims, Amount + References No definition available. + Details
Name: | wrb_LiabilityForClaimsAndClaimsAdjustmentExpenseNetOfReinsuranceIncurredButNotReportedIBNRClaimsAmount
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Liability for Claims and Claims Adjustment Expense, Net Of Reinsurance, Reported Claims, Amount + References No definition available. + Details
Name: | wrb_LiabilityForClaimsAndClaimsAdjustmentExpenseNetOfReinsuranceReportedClaimsAmount
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims Undiscounted Basis Prior Years, Increase (Decrease) + References No definition available. + Details
Name: | wrb_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsUndiscountedBasisPriorYearsIncreaseDecrease
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Liability for Claims and Claims Adjustment Expense, Net Of Reinsurance + References No definition available. + Details
Name: | wrb_LiabilityforClaimsandClaimsAdjustmentExpenseNetOfReinsurance
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Unfavorable Reserve Development Net Of Premium Offsets + References No definition available. + Details
Name: | wrb_UnfavorableReserveDevelopmentNetOfPremiumOffsets
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Workers' Compensation Discount, Current Year Amount + References No definition available. + Details
Name: | wrb_WorkersCompensationDiscountCurrentYearAmount
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=wrb_InsuranceDomesticSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=wrb_ReinsuranceandMonolineExcessSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |