XML 53 R42.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Significant Transactions - Bamboo (Details) - USD ($) $ in Millions |  | 3 Months Ended |
--- | --- | --- | ---
Jan. 02, 2024 | Dec. 31, 2022 | Mar. 31, 2024
Bamboo Ide8 Insurance Services LLC |  |  |
Other Significant Transactions [Line Items] |  |  |
Assets and goodwill acquired | $ 479.5 |  |
Liabilities acquired | 91.7 |  |
Noncontrolling interest acquired | 111.1 |  |
Total goodwill and other intangible assets | 371.4 |  |
Transaction costs | 4.0 |  | $ 0.3
Bamboo Ide8 Insurance Services LLC |  |  |
Other Significant Transactions [Line Items] |  |  |
Contributions to subsidiaries | 296.7 |  |
Contribution of primary capital | 36.0 |  |
Cash contributions for transaction | $ 20.0 |  |
Basic ownership | 72.80% |  |
Ownership percentage, after equity incentives | 63.70% |  |
Bamboo Ide8 Insurance Services LLC | Bamboo Management |  |  |
Other Significant Transactions [Line Items] |  |  |
Basic ownership | 16.10% |  |
Ownership percentage, after equity incentives | 26.60% |  |
Outrigger Re |  |  |
Other Significant Transactions [Line Items] |  |  |
Contributions to subsidiaries |  | $ 205.0 |

X
- Definition Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition. + References No definition available. + Details
Name: | us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479907/805-20-50-1 + Details
Name: | us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of liabilities assumed at the acquisition date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479907/805-20-50-1 + Details
Name: | us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The cash outflow associated with the acquisition of or advances to an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, and joint venture or equity method investment) or the acquisition of an additional interest in a subsidiary (controlled entity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-13 + Details
Name: | us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Goodwill + References No definition available. + Details
Name: | wtm_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndGoodwill
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets Including Goodwill + References No definition available. + Details
Name: | wtm_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsIncludingGoodwill
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Other Significant Transactions [Line Items] + References No definition available. + Details
Name: | wtm_OtherSignificantTransactionsLineItems
Namespace Prefix: | wtm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payments To Acquire Interest In Subsidiaries And Affiliates, Primary Capital + References No definition available. + Details
Name: | wtm_PaymentsToAcquireInterestInSubsidiariesAndAffiliatesPrimaryCapital
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Payments To Acquire Interest In Subsidiaries And Affiliates, Retirement Of Debt + References No definition available. + Details
Name: | wtm_PaymentsToAcquireInterestInSubsidiariesAndAffiliatesRetirementOfDebt
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Subsidiary, Ownership Percentage, Parent, After Equity Incentives + References No definition available. + Details
Name: | wtm_SubsidiaryOwnershipPercentageParentAfterEquityIncentives
Namespace Prefix: | wtm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=wtm_BambooIde8InsuranceServicesLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=wtm_BambooIde8InsuranceServicesLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=wtm_BambooManagementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_OwnershipAxis=wtm_OutriggerReMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |