XML 100 R87.htm IDEA: XBRL DOCUMENT
v3.22.4

Fixed Maturity Securities in an Unrealized Loss Position (Non-Investment Grade Fixed Maturity Securities) (Details) - External Credit Rating, Non Investment Grade $ in Thousands | Dec. 31, 2022 USD ($)
--- | ---
Foreign government |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 1
Aggregate Fair Value | $ 16
Gross Unrealized Loss | $ 10
Corporate |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 14
Aggregate Fair Value | $ 4,464
Gross Unrealized Loss | $ 269
Mortgage- Backed |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 10
Aggregate Fair Value | $ 39,347
Gross Unrealized Loss | $ 4,649
Asset-backed securities |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 1
Aggregate Fair Value | $ 12,247
Gross Unrealized Loss | $ 2,756
Debt Securities |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 62
Aggregate Fair Value | $ 175,406
Gross Unrealized Loss | $ 81,584
State and municipal |
Debt Securities, Available-for-sale [Line Items] |
Number of Securities | 36
Aggregate Fair Value | $ 119,332
Gross Unrealized Loss | $ 73,900

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

X
- Definition Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position + References No definition available. + Details
Name: | wrb_DebtSecuritiesAvailableforsaleandHeldtomaturityUnrealizedLossPosition
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position, Accumulated Loss + References No definition available. + Details
Name: | wrb_DebtSecuritiesAvailableforsaleandHeldtomaturityUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale and Held-to-maturity, Unrealized Loss Position, Number of Positions + References No definition available. + Details
Name: | wrb_DebtSecuritiesAvailableforsaleandHeldtomaturityUnrealizedLossPositionNumberofPositions
Namespace Prefix: | wrb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_ExternalCreditRatingByGroupingAxis=us-gaap_ExternalCreditRatingNonInvestmentGradeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |