XML 157 R141.htm IDEA: XBRL DOCUMENT
v3.22.4

SCHEDULE III SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
HG Global-BAM |  |  |
SUPPLEMENTARY INSURANCE INFORMATION |  |  |
Deferred Acquisition Costs | $ 36.0 | $ 33.1 | $ 27.8
Future Policy Benefits, Losses, Claims and Loss Expenses | 0.0 | 0.0 | 0.0
Unearned Premiums | 298.3 | 266.3 | 237.5
Other Policy Claims and Benefits Payable | 0.0 | 0.0 | 0.0
Premiums Earned | 33.3 | 26.9 | 22.8
Net Investment Income | 21.5 | 17.5 | 19.5
Benefits, Claims, Losses and Settlement Expenses | 0.0 | 0.0 | 0.0
Amortization of Deferred Acquisition Costs | 11.2 | 8.3 | 7.0
Other Operating Expenses | 0.4 | 0.4 | 0.4
Premiums Written | 65.1 | 55.8 | $ 61.7
Ark |  |  |
SUPPLEMENTARY INSURANCE INFORMATION |  |  |
Deferred Acquisition Costs | 127.2 | 100.8 |
Future Policy Benefits, Losses, Claims and Loss Expenses | 1,296.5 | 894.7 |
Unearned Premiums | 623.2 | 495.9 |
Other Policy Claims and Benefits Payable | 0.0 | 0.0 |
Premiums Earned | 1,043.4 | 637.3 |
Net Investment Income | 16.3 | 2.9 |
Benefits, Claims, Losses and Settlement Expenses | 536.4 | 314.8 |
Amortization of Deferred Acquisition Costs | 238.3 | 111.3 |
Other Operating Expenses | 78.7 | 64.6 |
Premiums Written | $ 1,195.2 | $ 859.1 |

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: | srt_SupplementaryInsuranceInformationBySegmentLineItems
Namespace Prefix: | srt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of amortization of deferred policy acquisition cost recognized, as disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column I)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of insurance benefit, claim, loss and settlement expenses incurred, as disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column H)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of deferred policy acquisition cost capitalized on contract remaining in force, as disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column B)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of reserve for future policy claim payable and loss expense to be incurred, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column C)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of net investment income earned, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column G)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of operating expense classified as other, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column J)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of claim and benefit payable classified as other, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column E)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of premium revenue earned, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column F)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationPremiumRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after premiums ceded and assumed, of premium written, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column K)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationPremiumsWritten
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of premium not yet earned, disclosed in supplementary insurance information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column D)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574960-122915 + Details
Name: | us-gaap_SupplementaryInsuranceInformationUnearnedPremiums
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

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