XML 100 R86.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Reserves For Losses And Loss Expenses (Reconciliation of Net Incurred and Paid Claims Development to Reserves for Loss and Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | $ 16,051,744 |  |
Total due from reinsurers on unpaid claims | 3,077,832 |  |
Total loss reserve discount | (389,924) |  |
Gross reserves at end of year | 18,739,652 | $ 17,011,223 | $ 15,390,888
Other liability |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 6,371,675 |  |
Workers' compensation |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,812,508 |  |
Professional liability |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,971,299 |  |
Auto |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,452,830 |  |
Short-tail lines |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 771,268 |  |
Casualty |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 2,174,132 |  |
Monoline excess |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,071,431 |  |
Property |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 275,397 |  |
Insurance |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 12,530,784 |  |
Total due from reinsurers on unpaid claims | 2,867,620 |  |
Total loss reserve discount | (12,193) |  |
Insurance | Other liability |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 6,371,675 |  |
Total due from reinsurers on unpaid claims | 951,773 |  |
Total loss reserve discount | 0 |  |
Insurance | Workers' compensation |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,812,508 |  |
Total due from reinsurers on unpaid claims | 189,182 |  |
Total loss reserve discount | (12,193) |  |
Insurance | Professional liability |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,971,299 |  |
Total due from reinsurers on unpaid claims | 1,138,129 |  |
Total loss reserve discount | 0 |  |
Insurance | Auto |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,452,830 |  |
Total due from reinsurers on unpaid claims | 81,334 |  |
Total loss reserve discount | 0 |  |
Insurance | Short-tail lines |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 771,268 |  |
Total due from reinsurers on unpaid claims | 379,621 |  |
Total loss reserve discount | 0 |  |
Insurance | Other |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 151,204 |  |
Total due from reinsurers on unpaid claims | 127,581 |  |
Total loss reserve discount | 0 |  |
Reinsurance & Monoline Excess |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 3,520,960 |  |
Total due from reinsurers on unpaid claims | 210,212 |  |
Total loss reserve discount | (377,731) |  |
Reinsurance & Monoline Excess | Casualty |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 2,174,132 |  |
Total due from reinsurers on unpaid claims | 116,198 |  |
Total loss reserve discount | (72,503) |  |
Reinsurance & Monoline Excess | Monoline excess |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 1,071,431 |  |
Total due from reinsurers on unpaid claims | 40,467 |  |
Total loss reserve discount | 305,228 |  |
Reinsurance & Monoline Excess | Property |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |
Total undiscounted reserves for loss and loss expenses, net of reinsurance | 275,397 |  |
Total due from reinsurers on unpaid claims | 53,547 |  |
Total loss reserve discount | $ 0 |  |

X
- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479584/944-310-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479838/944-20-50-5 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479616/944-310-45-6 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
Name: | us-gaap_ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cumulative discount related to the time value of money deducted from short-duration insurance contract liabilities that are reported at present value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (c) -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-5 + Details
Name: | us-gaap_ShortdurationInsuranceContractsDiscountedLiabilitiesAggregateDiscount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4B -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4B Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4C -SubTopic 40 -Topic 944 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-4C + Details
Name: | us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_ShortdurationInsuranceContractsReconciliationOfClaimsDevelopmentToLiabilityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_OtherLiabilityInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_WorkersCompensationInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_ProfessionalLiabilityInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_CommercialAutomobileInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_ShorttailInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_CasualtyInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=wrb_MonolineExcessProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_PropertyInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_OtherInsuranceProductLineMember
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: |