XML 34 R9.htm IDEA: XBRL DOCUMENT
v3.25.4

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Interest payments received | $ 10.8 | $ 5.8 |  |
Cash sold in subsidiary transaction | 0.0 | 4.2 | $ 0.0 |
Cash acquired from acquisition | 1.9 | 44.9 | 0.0 |
Restricted cash balance | 1.2 | 14.1 | 0.7 | $ 18.3
Unrestricted cash held for sale | 0.7 | 16.0 | 0.0 | 0.0
Restricted cash held for sale | 0.0 | 59.5 | 0.0 | $ 0.0
Other Operations |  |  |  |
Cash sold in subsidiary transaction | $ 135.0 | $ 0.0 | $ 0.8 |

X
- Definition The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-12 + Details
Name: | us-gaap_CashAcquiredFromAcquisition
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reduction in cash due to no longer including the former subsidiary's cash in the consolidated entity's cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-13 + Details
Name: | us-gaap_CashDivestedFromDeconsolidation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash and cash equivalent restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482913/230-10-50-8 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(1)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-4 + Details
Name: | us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Interest Income, Operating, Interest Payments Received + References No definition available. + Details
Name: | wtm_InterestIncomeOperatingInterestPaymentsReceived
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Restricted Cash, Held For Sale + References No definition available. + Details
Name: | wtm_RestrictedCashHeldForSale
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Unrestricted Cash, Held For Sale + References No definition available. + Details
Name: | wtm_UnrestrictedCashHeldForSale
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_CorporateNonSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |