XML 98 R84.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Net Investment Gains (Losses) (Change in Unrealized Gains (Losses) of Available For Sales Securities) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | $ 84,474 | $ 392,903 | $ (1,248,128)
Income tax (expense) benefit | (15,292) | (86,350) | 264,325
Noncontrolling interests | 2 | (2) | (2)
Total change in unrealized gains and losses | 69,184 | 306,551 | (983,805)
Debt Securities |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | 83,395 | 389,839 | (1,216,292)
Fixed maturity securities with allowance for expected credit losses |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | 4,428 | 643 | (28,370)
Investment funds |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | (3,217) | 3,989 | (2,019)
Other |  |  |
Realized and Unrealized Investment Gains Losses [Line Items] |  |  |
Unrealized investment gains, before tax | $ (132) | $ (1,568) | $ (1,447)

X
- Definition Amount, before tax and after adjustment, of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 10A -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 10A -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-10A Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-11 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Change in Unrealized Gain/(loss) on Investments, Including Portion Attributable to Noncontrolling Interest + References No definition available. + Details
Name: | wrb_ChangeinUnrealizedGainlossonInvestmentsIncludingPortionAttributabletoNoncontrollingInterest
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Change in Unrealized Gain/(loss) on Investments, Including Portion Attributable to Noncontrolling Interest, Net of Tax + References No definition available. + Details
Name: | wrb_ChangeinUnrealizedGainlossonInvestmentsIncludingPortionAttributabletoNoncontrollingInterestNetofTax
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Change in Unrealized Gain/(loss) on Investments, tax + References No definition available. + Details
Name: | wrb_ChangeinUnrealizedGainlossonInvestmentstax
Namespace Prefix: | wrb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Realized and Unrealized Investment Gains Losses [Line Items] + References No definition available. + Details
Name: | wrb_RealizedandUnrealizedInvestmentGainsLossesLineItems
Namespace Prefix: | wrb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

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

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

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