Company Quick10K Filing
White Mountains Insurance Group
Price1,077.60 EPS104
Shares3 P/E10
MCap3,433 P/FCF-47
Net Debt81 EBIT354
TEV3,514 TEV/EBIT10
TTM 2019-09-30, in MM, except price, ratios
10-Q 2020-06-30 Filed 2020-08-07
10-Q 2020-03-31 Filed 2020-05-08
10-K 2019-12-31 Filed 2020-03-02
10-Q 2019-09-30 Filed 2019-11-06
10-Q 2019-06-30 Filed 2019-08-06
10-Q 2019-03-31 Filed 2019-05-06
10-K 2018-12-31 Filed 2019-02-27
10-Q 2018-09-30 Filed 2018-11-05
10-Q 2018-06-30 Filed 2018-08-07
10-Q 2018-03-31 Filed 2018-05-02
10-K 2017-12-31 Filed 2018-02-28
10-Q 2017-09-30 Filed 2017-11-08
10-Q 2017-06-30 Filed 2017-08-04
10-Q 2017-03-31 Filed 2017-05-02
10-K 2016-12-31 Filed 2017-02-27
10-Q 2016-09-30 Filed 2016-11-02
10-Q 2016-06-30 Filed 2016-08-03
10-Q 2016-03-31 Filed 2016-05-02
10-K 2015-12-31 Filed 2016-02-29
10-Q 2015-09-30 Filed 2015-11-02
10-Q 2015-06-30 Filed 2015-08-03
10-Q 2015-03-31 Filed 2015-05-04
10-K 2014-12-31 Filed 2015-02-27
10-Q 2014-09-30 Filed 2014-10-29
10-Q 2014-06-30 Filed 2014-07-29
10-Q 2014-03-31 Filed 2014-04-28
10-K 2013-12-31 Filed 2014-02-28
10-Q 2013-09-30 Filed 2013-10-28
10-Q 2013-06-30 Filed 2013-07-30
10-Q 2013-03-31 Filed 2013-04-29
10-K 2012-12-31 Filed 2013-03-01
10-Q 2012-09-30 Filed 2012-10-30
10-Q 2012-06-30 Filed 2012-07-27
10-Q 2012-03-31 Filed 2012-04-27
10-Q 2011-09-30 Filed 2011-10-28
10-Q 2011-06-30 Filed 2011-07-29
10-Q 2011-03-31 Filed 2011-04-29
10-K 2010-12-31 Filed 2011-02-28
10-Q 2010-09-30 Filed 2010-10-29
10-Q 2010-06-30 Filed 2010-07-30
10-Q 2010-03-31 Filed 2010-04-29
10-K 2009-12-31 Filed 2010-02-26
8-K 2020-08-07 Earnings, Exhibits
8-K 2020-05-21
8-K 2020-05-08
8-K 2020-04-07
8-K 2020-03-20
8-K 2020-02-05
8-K 2019-11-06
8-K 2019-08-29
8-K 2019-08-06
8-K 2019-06-28
8-K 2019-06-07
8-K 2019-05-24
8-K 2019-05-06
8-K 2019-04-04
8-K 2019-02-27
8-K 2019-02-26
8-K 2019-02-14
8-K 2019-02-06
8-K 2019-02-04
8-K 2019-01-03
8-K 2018-11-05
8-K 2018-08-23
8-K 2018-08-07
8-K 2018-06-08
8-K 2018-05-24
8-K 2018-05-11
8-K 2018-05-02
8-K 2018-04-10
8-K 2018-03-31
8-K 2018-03-01
8-K 2018-02-07

WTM 10Q Quarterly Report

Part I.Financial Information.
Item 1. Financial Statements
Note 1. Basis of Presentation and Significant Accounting Policies
Note 2. Significant Transactions
Note 3. Investment Securities
Note 4. Goodwill and Other Intangible Assets
Note 5. Debt
Note 6. Income Taxes
Note 7. Derivatives
Note 8. Municipal Bond Guarantee Insurance
Note 9. Earnings per Share
Note 10. Employee Share - Based Incentive Compensation Plans
Note 11. Leases
Note 12. Non - Controlling Interests
Note 13. Segment Information
Note 14. Equity - Method Eligible Investments
Note 15. Fair Value of Financial Instruments
Note 16. Commitments and Contingencies
Note 18. Subsequent Events
Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations.
Item 3. Quantitative and Qualitative Disclosures About Market Risk.
Item 4. Controls and Procedures.
Part II. Other Information
Item 1. Legal Proceedings.
Item 1A. Risk Factors.
Item 2. Issuer Purchases of Equity Securities.
Item 3. Defaults Upon Senior Securities.
Item 4. Mine Safety Disclosures.
Item 5. Other Information.
Item 6. Exhibits.
EX-31.1 wtmq22020ex311.htm
EX-31.2 wtmq22020ex312.htm
EX-32.1 wtmq22020ex321.htm
EX-32.2 wtmq22020ex322.htm

White Mountains Insurance Group Earnings 2020-06-30

Balance SheetIncome StatementCash Flow
151296302012201420172020
Assets, Equity
0.70.50.40.20.1-0.12012201420172020
Rev, G Profit, Net Income
0.80.50.2-0.2-0.5-0.82012201420172020
Ops, Inv, Fin

Document
false--12-31Q2201900007768673000000260000012800000119000001.001.00500000005000000031853533101761318535331017610.03000.8960.9660.3840.3000.6240.1000.0320.1750.4950.3650.3500.6230.0940.0320.1434242165000002600000500000006080000056300000963000005630000096300000P3YP5Y0.4270.220.320.090.150.250.040.23000.12000.18000.0600126126 0000776867 2020-01-01 2020-06-30 0000776867 2020-08-05 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 wtm:HgGlobalBamMember 2019-12-31 0000776867 wtm:OtherEntityMember 2019-12-31 0000776867 wtm:OtherEntityMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:HgGlobalBamMember 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-03-31 0000776867 2020-03-31 0000776867 wtm:OtherEntityMember 2019-01-01 2019-06-30 0000776867 wtm:MediaAlphaMember 2019-04-01 2019-06-30 0000776867 wtm:OtherEntityMember 2019-04-01 2019-06-30 0000776867 2019-01-01 2019-06-30 0000776867 wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 2020-04-01 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:OtherEntityMember 2020-01-01 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-04-01 2020-06-30 0000776867 wtm:OtherEntityMember 2020-04-01 2020-06-30 0000776867 wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 2019-04-01 2019-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-04-01 2019-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaMember 2020-04-01 2020-06-30 0000776867 wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 us-gaap:RetainedEarningsMember 2020-01-01 2020-06-30 0000776867 us-gaap:ParentMember 2020-01-01 2020-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:ParentMember 2020-01-01 2020-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-01-01 2020-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2020-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-12-31 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2020-01-01 2020-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2020-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:NoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 us-gaap:RetainedEarningsMember 2019-12-31 0000776867 wtm:BamMember us-gaap:NoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 wtm:BamMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 us-gaap:ParentMember 2020-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2019-12-31 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-12-31 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2019-12-31 0000776867 us-gaap:ParentMember 2019-12-31 0000776867 us-gaap:ForeignCurrencyGainLossMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-01-01 2020-06-30 0000776867 us-gaap:RetainedEarningsMember 2020-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-01-01 2019-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2019-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-01-01 2019-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2019-01-01 2019-06-30 0000776867 wtm:MediaAlphaMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:RetainedEarningsMember 2019-01-01 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 wtm:BamMember us-gaap:NoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 wtm:BamMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:ParentMember 2019-01-01 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:ParentMember 2019-01-01 2019-06-30 0000776867 us-gaap:RetainedEarningsMember 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:NoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2018-12-31 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2018-12-31 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2018-12-31 0000776867 us-gaap:ParentMember 2018-12-31 0000776867 us-gaap:ParentMember 2019-06-30 0000776867 us-gaap:RetainedEarningsMember 2018-12-31 0000776867 us-gaap:NoncontrollingInterestMember 2018-12-31 0000776867 wtm:MediaAlphaMember us-gaap:NoncontrollingInterestMember 2019-01-01 2019-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 us-gaap:RetainedEarningsMember 2019-03-31 0000776867 us-gaap:NoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 us-gaap:RetainedEarningsMember 2019-04-01 2019-06-30 0000776867 us-gaap:NoncontrollingInterestMember 2019-03-31 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-04-01 2019-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2019-04-01 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-04-01 2019-06-30 0000776867 us-gaap:ParentMember 2019-04-01 2019-06-30 0000776867 us-gaap:ParentMember 2019-03-31 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2019-03-31 0000776867 wtm:BamMember us-gaap:NoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 wtm:BamMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-03-31 0000776867 us-gaap:ForeignCurrencyGainLossMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2019-03-31 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:ParentMember 2019-04-01 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:NoncontrollingInterestMember 2019-04-01 2019-06-30 0000776867 us-gaap:ParentMember 2020-04-01 2020-06-30 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 wtm:BamMember wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 us-gaap:RetainedEarningsMember 2020-04-01 2020-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2020-03-31 0000776867 us-gaap:NoncontrollingInterestMember 2020-03-31 0000776867 wtm:TotalEquityIncludesNoncontrollingInterestMember 2020-03-31 0000776867 us-gaap:NoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 us-gaap:CommonStockIncludingAdditionalPaidInCapitalMember 2020-04-01 2020-06-30 0000776867 us-gaap:RetainedEarningsMember 2020-03-31 0000776867 wtm:BamMember us-gaap:NoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-04-01 2020-06-30 0000776867 us-gaap:ParentMember 2020-03-31 0000776867 us-gaap:AccumulatedOtherComprehensiveIncomeMember 2020-03-31 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:NoncontrollingInterestMember 2020-04-01 2020-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember us-gaap:ParentMember 2020-04-01 2020-06-30 0000776867 2019-06-30 0000776867 2018-12-31 0000776867 2020-01-01 2020-03-31 0000776867 wtm:NSMInsuranceHoldCoLLCMember 2019-12-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-10-01 2019-12-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-04-03 0000776867 wtm:KuduMember wtm:KuduDebtMember wtm:DelayedDrawTermLoansMember 2019-12-31 0000776867 wtm:HgGlobalMember wtm:SeriesABAMSurplusNoteMember 2012-07-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-04-04 0000776867 wtm:HgGlobalMember wtm:SeriesBBAMSurplusNoteMember 2012-07-31 0000776867 us-gaap:AccountingStandardsUpdate201602Member 2019-01-01 0000776867 us-gaap:AccountingStandardsUpdate201602Member 2020-06-30 0000776867 2019-04-04 2019-04-04 0000776867 wtm:NSMInsuranceHoldCoLLCMember 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 wtm:HgGlobalMember us-gaap:PreferredStockMember 2020-06-30 0000776867 wtm:HgGlobalMember 2012-07-31 0000776867 wtm:HgGlobalMember 2020-06-30 0000776867 wtm:HgGlobalMember us-gaap:CommonStockMember 2020-06-30 0000776867 wtm:HgGlobalMember us-gaap:PreferredStockMember 2019-12-31 0000776867 wtm:HgGlobalMember us-gaap:CommonStockMember 2019-12-31 0000776867 wtm:MediaAlphaMember 2019-01-01 2019-03-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember 2018-05-18 0000776867 wtm:NSMInsuranceGroupMember currency:USD wtm:KingsbridgeMember 2020-04-07 2020-04-07 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember 2018-05-18 2018-05-18 0000776867 wtm:NSMInsuranceGroupMember wtm:EmbracePetInsuranceMember 2019-04-01 2019-04-01 0000776867 2020-05-07 2020-05-07 0000776867 wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:KingsbridgeMember 2020-04-07 0000776867 wtm:KuduInvestmentManagementLLCMember 2018-02-05 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 wtm:AIGCollectorCarBusinessMember 2019-06-28 0000776867 wtm:AIGCollectorCarBusinessMember 2019-06-28 2019-06-28 0000776867 wtm:WhiteMountainsMember wtm:AIGCollectorCarBusinessMember 2019-06-28 2019-06-28 0000776867 wtm:NSMInsuranceHoldCoLLCMember 2018-05-11 2018-05-11 0000776867 wtm:KBKInsuranceGroupInc.KBKPremiumServicesInc.Member 2019-03-31 0000776867 wtm:MediaAlphaMember 2019-02-26 0000776867 wtm:NSMInsuranceGroupMember wtm:AIGCollectorCarBusinessMember 2019-06-28 2019-06-28 0000776867 wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember 2020-01-01 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:EmbracePetInsuranceMember 2019-04-01 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceHoldCoLLCMember 2018-05-11 0000776867 wtm:NSMInsuranceGroupMember wtm:KingsbridgeMember 2020-04-07 2020-04-07 0000776867 wtm:KBKInsuranceGroupInc.KBKPremiumServicesInc.Member 2018-12-03 0000776867 wtm:NSMBankFacilityMember 2018-05-11 0000776867 wtm:KBKInsuranceGroupInc.KBKPremiumServicesInc.Member 2018-12-03 2018-12-03 0000776867 wtm:NSMInsuranceGroupMember currency:GBP wtm:KingsbridgeMember 2020-04-07 2020-04-07 0000776867 wtm:MediaAlphaMember 2018-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:EmbracePetInsuranceMember 2019-04-01 0000776867 wtm:NSMInsuranceHoldCoLLCMember 2018-12-03 2018-12-03 0000776867 2018-02-05 0000776867 wtm:InsuranceLinkedSecuritiesFundsMember 2019-05-31 0000776867 wtm:ElementumHoldingsL.P.Member 2019-05-31 0000776867 wtm:KuduMember wtm:KuduDebtMember wtm:DelayedDrawTermLoansMember 2020-06-30 0000776867 wtm:MediaAlphaMember 2020-01-01 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:ElementumFundsMember 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-02-26 2019-02-26 0000776867 wtm:NSMInsuranceGroupMember 2018-05-11 2018-09-30 0000776867 us-gaap:CommonStockMember 2019-12-31 0000776867 wtm:OtherLongTermInvestmentsExcludingEquityMethodInvestmentsMember 2019-01-01 2019-12-31 0000776867 wtm:OtherLongTermInvestmentsExcludingEquityMethodInvestmentsMember 2019-12-31 0000776867 us-gaap:CommonStockMember 2019-01-01 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member 2019-01-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2019-01-01 2019-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2019-01-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel1Member 2019-01-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel2Member 2018-12-31 0000776867 us-gaap:FairValueInputsLevel2Member 2019-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2018-12-31 0000776867 us-gaap:FairValueInputsLevel1Member 2019-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2018-12-31 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2019-06-30 0000776867 us-gaap:FairValueInputsLevel1Member 2018-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2019-06-30 0000776867 wtm:ZillionInsuranceServicesMember 2020-04-01 2020-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember 2020-01-01 2020-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember 2019-04-01 2019-06-30 0000776867 srt:MaximumMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2019-01-01 2019-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2019-06-30 0000776867 us-gaap:ForeignCurrencyGainLossMember 2020-04-01 2020-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember 2019-01-01 2019-06-30 0000776867 us-gaap:PrivateEquityFundsMember 2020-06-30 0000776867 srt:MinimumMember 2020-01-01 2020-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2019-12-31 0000776867 us-gaap:ShortTermInvestmentsMember 2018-12-31 0000776867 wtm:InsuranceLinkedSecuritiesFundsMember 2020-06-30 0000776867 2019-01-01 2019-12-31 0000776867 wtm:NoblrMember 2019-12-31 0000776867 wtm:HedgeFundsAndPrivateEquityFundsMember 2020-06-30 0000776867 us-gaap:CommonStockMember 2020-06-30 0000776867 wtm:HedgeFundsAndPrivateEquityFundsMember 2019-12-31 0000776867 us-gaap:ShortTermInvestmentsMember 2020-06-30 0000776867 wtm:PassportDavidShieldMember 2020-04-01 2020-06-30 0000776867 wtm:NoblrMember 2020-06-30 0000776867 us-gaap:HedgeFundsMember us-gaap:HedgeFundsMember 2020-01-01 2020-03-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2020-01-01 2020-06-30 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2020-01-01 2020-06-30 0000776867 wtm:EstimatedNetRealizableValueMember wtm:StandardPoorsNrRatingMember wtm:Compare.comMember 2020-06-30 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:ZillionInsuranceServicesMember 2020-06-30 0000776867 wtm:EstimatedNetRealizableValueMember wtm:StandardPoorsNrRatingMember wtm:Compare.comMember 2020-06-30 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:NoblrIncMember 2020-06-30 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:NoblrIncMember 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2020-06-30 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2020-06-30 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:ZillionInsuranceServicesMember 2020-06-30 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2020-01-01 2020-06-30 0000776867 us-gaap:MeasurementInputLongTermRevenueGrowthRateMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2020-06-30 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2020-06-30 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2020-01-01 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2020-06-30 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2020-06-30 0000776867 us-gaap:MeasurementInputLongTermRevenueGrowthRateMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:EquitySecuritiesMember 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:EquitySecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasuredAtNetAssetValuePerShareMember wtm:HedgeFundsAndPrivateEquityFundsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:EquitySecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsAARatingMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsARatingMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 srt:StandardPoorsAAARatingMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 srt:StandardPoorsBBRatingMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 srt:StandardPoorsAARatingMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 srt:StandardPoorsBBBRatingMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsBBRatingMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsAAARatingMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsBBBRatingMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 srt:StandardPoorsARatingMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 wtm:AerospaceDefenseGovernmentMember us-gaap:PrivateEquityFundsMember 2019-12-31 0000776867 us-gaap:PrivateEquityFundsMember us-gaap:PrivateEquityFundsMember 2019-12-31 0000776867 wtm:HedgeFundLongShortEquityBanksandFinancialMember us-gaap:HedgeFundsMember 2019-12-31 0000776867 wtm:FinancialServicesMember us-gaap:PrivateEquityFundsMember 2020-06-30 0000776867 wtm:HedgeFundLongShortEquityBanksandFinancialMember us-gaap:HedgeFundsMember 2020-06-30 0000776867 us-gaap:HedgeFundsMember us-gaap:HedgeFundsMember 2020-06-30 0000776867 us-gaap:PrivateEquityFundsMember us-gaap:PrivateEquityFundsMember 2020-06-30 0000776867 wtm:FinancialServicesMember us-gaap:PrivateEquityFundsMember 2019-12-31 0000776867 wtm:AerospaceDefenseGovernmentMember us-gaap:PrivateEquityFundsMember 2020-06-30 0000776867 us-gaap:HedgeFundsMember us-gaap:HedgeFundsMember 2019-12-31 0000776867 wtm:PrivateEquityFundsManufacturingAndIndustrialMember us-gaap:PrivateEquityFundsMember 2020-06-30 0000776867 wtm:PrivateEquityFundsManufacturingAndIndustrialMember us-gaap:PrivateEquityFundsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember wtm:OtherLongTermInvestmentNAVMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember wtm:OtherLongTermInvestmentNAVMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember wtm:OtherLongTermInvestmentNAVMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember wtm:OtherLongTermInvestmentNAVMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2020-06-30 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2020-06-30 0000776867 us-gaap:PrivateEquityFundsMember wtm:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLiquidatingInvestmentRemainingPeriodOver10YearsMember 2020-06-30 0000776867 us-gaap:PrivateEquityFundsMember wtm:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLiquidatingInvestmentRemainingPeriod3To5YearsMember 2020-06-30 0000776867 us-gaap:PrivateEquityFundsMember wtm:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLiquidatingInvestmentRemainingPeriod5To10YearsMember 2020-06-30 0000776867 us-gaap:PrivateEquityFundsMember wtm:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLiquidatingInvestmentRemainingPeriod1To3YearsMember 2020-06-30 0000776867 us-gaap:CommonStockMember 2020-01-01 2020-06-30 0000776867 wtm:OtherLongTermInvestmentsExcludingEquityMethodInvestmentsMember 2020-01-01 2020-06-30 0000776867 wtm:OtherLongTermInvestmentsExcludingEquityMethodInvestmentsMember 2020-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2020-04-01 2020-06-30 0000776867 us-gaap:CommonStockMember 2019-01-01 2019-06-30 0000776867 us-gaap:FixedMaturitiesMember 2020-01-01 2020-06-30 0000776867 us-gaap:ShortTermInvestmentsMember 2019-04-01 2019-06-30 0000776867 us-gaap:OtherLongTermInvestmentsMember 2020-01-01 2020-06-30 0000776867 us-gaap:FixedMaturitiesMember 2020-04-01 2020-06-30 0000776867 us-gaap:OtherLongTermInvestmentsMember 2019-01-01 2019-06-30 0000776867 us-gaap:FixedMaturitiesMember 2019-04-01 2019-06-30 0000776867 us-gaap:OtherLongTermInvestmentsMember 2019-04-01 2019-06-30 0000776867 us-gaap:OtherLongTermInvestmentsMember 2020-04-01 2020-06-30 0000776867 us-gaap:CommonStockMember 2020-04-01 2020-06-30 0000776867 us-gaap:FixedMaturitiesMember 2019-01-01 2019-06-30 0000776867 us-gaap:CommonStockMember 2019-04-01 2019-06-30 0000776867 us-gaap:MeasurementInputLongTermRevenueGrowthRateMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2019-12-31 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:NoblrIncMember 2019-12-31 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:NoblrIncMember 2019-12-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2019-12-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2019-01-01 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-12-31 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:ZillionInsuranceServicesMember 2019-12-31 0000776867 wtm:EstimatedNetRealizableValueMember wtm:StandardPoorsNrRatingMember wtm:Compare.comMember 2019-12-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:MediaAlphaMember 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2019-12-31 0000776867 us-gaap:MeasurementInputLongTermRevenueGrowthRateMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2019-12-31 0000776867 wtm:DiscountedCashFlowValuationTechniqueMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2019-12-31 0000776867 wtm:EstimatedNetRealizableValueMember wtm:StandardPoorsNrRatingMember wtm:Compare.comMember 2019-12-31 0000776867 wtm:RecenttransactionMember wtm:StandardPoorsNrRatingMember wtm:ZillionInsuranceServicesMember 2019-12-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:DavidShieldPassportCardMember 2019-01-01 2019-12-31 0000776867 us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:ElementumHoldingsL.P.Member 2019-01-01 2019-12-31 0000776867 wtm:InvestmentsHeldMember 2019-04-01 2019-06-30 0000776867 wtm:InvestmentsHeldMember 2020-01-01 2020-06-30 0000776867 us-gaap:EquitySecuritiesMember 2020-04-01 2020-06-30 0000776867 us-gaap:EquitySecuritiesMember 2019-01-01 2019-06-30 0000776867 wtm:InvestmentsHeldMember 2020-04-01 2020-06-30 0000776867 us-gaap:EquitySecuritiesMember 2020-01-01 2020-06-30 0000776867 wtm:InvestmentsHeldMember 2019-01-01 2019-06-30 0000776867 us-gaap:EquitySecuritiesMember 2019-04-01 2019-06-30 0000776867 wtm:InsurancelinkedSecuritiesMember 2019-12-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 wtm:WhiteMountainsMember 2020-06-30 0000776867 wtm:ElementumHoldingsL.P.Member 2020-06-30 0000776867 wtm:PrivateDebtInstrumentMember 2019-12-31 0000776867 wtm:TotalUnconsolidatedEntitiesMember 2019-12-31 0000776867 wtm:OtherUnconsolidatedPrivateEquityInvestmentsMember 2019-12-31 0000776867 wtm:DavidShieldPassportCardMember 2019-12-31 0000776867 wtm:InsurancelinkedSecuritiesMember 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-12-31 0000776867 wtm:ElementumHoldingsL.P.Member 2019-12-31 0000776867 wtm:DavidShieldPassportCardMember 2020-06-30 0000776867 wtm:PrivateDebtInstrumentMember 2020-06-30 0000776867 wtm:OtherUnconsolidatedPrivateEquityInvestmentsMember 2020-06-30 0000776867 wtm:MediaAlphaMember 2020-06-30 0000776867 wtm:TotalUnconsolidatedEntitiesMember 2020-06-30 0000776867 wtm:WhiteMountainsMember 2019-12-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2019-04-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel3Member 2020-01-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member 2020-04-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:OtherLongTermInvestmentsMember 2020-04-01 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member 2019-01-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel3Member 2019-04-01 2019-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2019-12-31 0000776867 us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2019-12-31 0000776867 us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:CollateralizedCreditCardSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:CollateralizedAutoLoansMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:CollateralizedAutoLoansMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2020-06-30 0000776867 us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2019-12-31 0000776867 us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2020-06-30 0000776867 us-gaap:MortgageBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:CollateralizedAutoLoansMember 2020-06-30 0000776867 us-gaap:CollateralizedAutoLoansMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:AssetBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2020-06-30 0000776867 us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:MortgageBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:MortgageBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:CollateralizedCreditCardSecuritiesMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember 2019-12-31 0000776867 us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember 2020-06-30 0000776867 us-gaap:MortgageBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:MortgageBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:CollateralizedCreditCardSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:CollateralizedCreditCardSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:CollateralizedAutoLoansMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2019-12-31 0000776867 us-gaap:FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember 2019-12-31 0000776867 us-gaap:CollateralizedCreditCardSecuritiesMember 2019-12-31 0000776867 us-gaap:CollateralizedAutoLoansMember 2020-06-30 0000776867 us-gaap:CollateralizedCreditCardSecuritiesMember 2020-06-30 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:MortgageBackedSecuritiesMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesMember 2019-01-01 2019-12-31 0000776867 us-gaap:USTreasuryAndGovernmentMember 2019-01-01 2019-12-31 0000776867 us-gaap:FixedIncomeInvestmentsMember 2019-01-01 2019-12-31 0000776867 us-gaap:MunicipalBondsMember 2019-12-31 0000776867 us-gaap:MunicipalBondsMember 2019-01-01 2019-12-31 0000776867 us-gaap:USTreasuryAndGovernmentMember 2019-12-31 0000776867 us-gaap:CorporateDebtSecuritiesMember 2019-01-01 2019-12-31 0000776867 us-gaap:FixedIncomeInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:IndustrialMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:FixedMaturitiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember us-gaap:OtherLongTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:UtilitiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:ExchangeTradedFundsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember us-gaap:EquitySecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:EquitySecuritiesMember wtm:OtherSectorMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:TechnologyMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember us-gaap:HealthCareMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:AssetBackedSecuritiesMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:BasicMaterialsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel1Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:ShortTermInvestmentsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:USTreasuryAndGovernmentMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:MunicipalBondsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:FinancialsMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:OtherLongTermInvestmentsMember wtm:OtherLongTermInvestmentNAVMember 2019-12-31 0000776867 us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:ConsumerMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:CommunicationsMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel3Member us-gaap:FairValueMeasurementsRecurringMember us-gaap:CorporateDebtSecuritiesMember wtm:EnergyMember 2019-12-31 0000776867 us-gaap:FairValueInputsLevel2Member us-gaap:FairValueMeasurementsRecurringMember 2019-12-31 0000776867 us-gaap:USTreasuryAndGovernmentMember 2020-06-30 0000776867 us-gaap:FixedIncomeInvestmentsMember 2020-06-30 0000776867 us-gaap:AssetBackedSecuritiesMember 2020-01-01 2020-06-30 0000776867 us-gaap:FixedIncomeInvestmentsMember 2020-01-01 2020-06-30 0000776867 us-gaap:MunicipalBondsMember 2020-06-30 0000776867 us-gaap:USTreasuryAndGovernmentMember 2020-01-01 2020-06-30 0000776867 us-gaap:CorporateDebtSecuritiesMember 2020-01-01 2020-06-30 0000776867 us-gaap:MunicipalBondsMember 2020-01-01 2020-06-30 0000776867 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2020-01-01 2020-06-30 0000776867 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2020-01-01 2020-06-30 0000776867 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2019-01-01 2019-12-31 0000776867 srt:MaximumMember wtm:TerminalMultipleMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2019-12-31 0000776867 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2020-01-01 2020-06-30 0000776867 srt:MinimumMember wtm:TerminalMultipleMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2019-12-31 0000776867 srt:MaximumMember wtm:TerminalMultipleMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2020-06-30 0000776867 srt:MinimumMember us-gaap:MeasurementInputRevenueMultipleMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2020-06-30 0000776867 srt:MinimumMember wtm:TerminalMultipleMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2020-06-30 0000776867 srt:MaximumMember us-gaap:MeasurementInputRevenueMultipleMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2020-06-30 0000776867 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2020-01-01 2020-06-30 0000776867 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:KuduInvestmentsMember 2019-01-01 2019-12-31 0000776867 srt:MinimumMember us-gaap:MeasurementInputRevenueMultipleMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-12-31 0000776867 srt:MaximumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2019-01-01 2019-12-31 0000776867 srt:MinimumMember us-gaap:MeasurementInputDiscountRateMember wtm:StandardPoorsNrRatingMember wtm:PrivateDebtInstrumentMember 2019-01-01 2019-12-31 0000776867 srt:MaximumMember us-gaap:MeasurementInputRevenueMultipleMember wtm:StandardPoorsNrRatingMember wtm:OtherMember 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:GoodwillMember 2020-01-01 2020-06-30 0000776867 wtm:EmbracePetInsuranceMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:GoodwillMember 2019-01-01 2019-12-31 0000776867 us-gaap:OtherIntangibleAssetsMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 us-gaap:GoodwillMember 2019-04-01 2019-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2019-03-31 0000776867 wtm:IntangibleAssetandGoodwillMember 2020-04-01 2020-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2019-04-01 2019-06-30 0000776867 wtm:RenewalRightsMember 2019-04-01 2019-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2019-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2020-04-01 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-04-01 2019-06-30 0000776867 us-gaap:GoodwillMember 2019-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-06-30 0000776867 us-gaap:GoodwillMember 2020-03-31 0000776867 us-gaap:OtherIntangibleAssetsMember 2020-06-30 0000776867 us-gaap:GoodwillMember 2020-06-30 0000776867 us-gaap:GoodwillMember 2020-04-01 2020-06-30 0000776867 us-gaap:GoodwillMember 2019-03-31 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-03-31 0000776867 wtm:IntangibleAssetandGoodwillMember 2020-03-31 0000776867 us-gaap:OtherIntangibleAssetsMember 2020-03-31 0000776867 us-gaap:TradeNamesMember wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 us-gaap:LicensingAgreementsMember wtm:OtherMember 2020-06-30 0000776867 wtm:OtherMember 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-12-31 0000776867 us-gaap:TradeNamesMember wtm:OtherMember 2020-01-01 2020-06-30 0000776867 us-gaap:LicensingAgreementsMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 wtm:OtherMember wtm:OtherMember 2020-06-30 0000776867 us-gaap:CustomerRelationshipsMember wtm:OtherMember 2020-01-01 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:OtherMember 2019-12-31 0000776867 us-gaap:CustomerRelationshipsMember wtm:OtherMember 2020-06-30 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:OtherMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 us-gaap:CustomerRelationshipsMember wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:OtherMember wtm:OtherMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 us-gaap:TradeNamesMember wtm:OtherMember 2020-06-30 0000776867 us-gaap:CustomerRelationshipsMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:InformationTechnologyMember wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:InformationTechnologyMember wtm:OtherMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember wtm:InformationTechnologyMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:InformationTechnologyMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:RenewalRightsMember wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 us-gaap:LicensingAgreementsMember wtm:OtherMember 2019-12-31 0000776867 us-gaap:CustomerRelationshipsMember wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:RenewalRightsMember wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:OtherMember 2019-12-31 0000776867 us-gaap:CustomerRelationshipsMember wtm:OtherMember 2019-12-31 0000776867 us-gaap:TradeNamesMember wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:InformationTechnologyMember wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:InformationTechnologyMember wtm:OtherMember 2020-06-30 0000776867 us-gaap:CustomerRelationshipsMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:RenewalRightsMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember us-gaap:OtherIntangibleAssetsMember 2020-01-01 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-01-01 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember wtm:RenewalRightsMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 us-gaap:TradeNamesMember wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:KuduInvestmentManagementLLCMember 2019-01-01 2019-12-31 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 wtm:OtherMember 2019-01-01 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember us-gaap:TradeNamesMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-12-31 0000776867 wtm:RenewalRightsMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember wtm:OtherMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:InformationTechnologyMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 wtm:FreshInsuranceServicesGroupLimitedMember us-gaap:CustomerRelationshipsMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 us-gaap:CustomerRelationshipsMember wtm:OtherMember 2019-01-01 2019-12-31 0000776867 wtm:InformationTechnologyMember wtm:OtherMember 2020-01-01 2020-06-30 0000776867 us-gaap:TradeNamesMember wtm:KuduInvestmentManagementLLCMember 2020-01-01 2020-06-30 0000776867 wtm:TermLoanMember 2020-01-01 2020-06-30 0000776867 wtm:WhiteMountainsMember 2020-01-01 2020-06-30 0000776867 us-gaap:GoodwillMember 2020-01-01 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2019-01-01 2019-06-30 0000776867 wtm:RenewalRightsMember 2019-01-01 2019-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2019-01-01 2019-06-30 0000776867 wtm:IntangibleAssetandGoodwillMember 2020-01-01 2020-06-30 0000776867 us-gaap:OtherIntangibleAssetsMember 2020-01-01 2020-06-30 0000776867 us-gaap:GoodwillMember 2019-01-01 2019-06-30 0000776867 us-gaap:GoodwillMember 2018-12-31 0000776867 wtm:IntangibleAssetandGoodwillMember 2018-12-31 0000776867 wtm:IntangibleAssetandGoodwillMember 2019-12-31 0000776867 us-gaap:GoodwillMember 2019-12-31 0000776867 us-gaap:OtherIntangibleAssetsMember 2018-12-31 0000776867 wtm:RenewalRightsMember 2020-01-01 2020-06-30 0000776867 wtm:KingsbridgeMember 2020-04-07 0000776867 wtm:OtherOperationsMember 2019-03-12 0000776867 wtm:RenewalRightsMember 2019-06-28 0000776867 wtm:KuduMember 2019-04-04 0000776867 wtm:OtherMember wtm:OtherMember wtm:TermLoanMember 2019-12-31 0000776867 wtm:KuduMember wtm:KuduDebtMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:KuduMember wtm:KuduDebtMember wtm:TermLoanMember 2019-12-31 0000776867 wtm:KuduMember wtm:KuduDebtMember 2019-12-31 0000776867 wtm:KuduMember wtm:KuduDebtMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:OtherNSMMember wtm:TermLoanMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:OtherNSMMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2019-12-31 0000776867 wtm:OtherMember wtm:OtherMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:TermLoanMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember srt:MinimumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember currency:GBP wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-04-07 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2020-06-30 0000776867 wtm:KuduMember srt:MaximumMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember srt:MinimumMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:PrimeRateMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:TermLoanMember 2020-01-01 2020-06-30 0000776867 2020-04-07 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:InterestRateSwapMember us-gaap:NondesignatedMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:InterestRateSwapMember us-gaap:DesignatedAsHedgingInstrumentMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember srt:MaximumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember srt:MinimumMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:TermLoanMember 2020-04-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:InterestRateSwapMember wtm:TermLoanMember 2018-06-15 0000776867 wtm:OtherOperationsMember us-gaap:RevolvingCreditFacilityMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember currency:GBP srt:MaximumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember srt:MaximumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember wtm:RenewalRightsMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2019-01-01 2019-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:PrimeRateMember 2020-01-01 2020-06-30 0000776867 wtm:OtherOperationsMember wtm:DelayedDrawTermLoansMember 2020-06-30 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember 2019-12-23 0000776867 wtm:OtherOperationsMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:InterestRateSwapMember wtm:TermLoanMember 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember currency:USD wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-04-07 0000776867 wtm:NSMInsuranceGroupMember currency:GBP srt:MinimumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-04-07 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:InterestRateSwapMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember srt:MinimumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-01-01 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2020-03-31 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:TermLoanMember 2019-12-23 0000776867 wtm:NSMInsuranceGroupMember wtm:EmbracePetInsuranceMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2020-04-07 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2019-12-23 0000776867 wtm:KuduMember wtm:KuduBankFacilityMember wtm:DelayedDrawTermLoansMember 2019-12-23 0000776867 wtm:NSMInsuranceGroupMember currency:GBP srt:MaximumMember wtm:NSMBankFacilityMember wtm:TermLoanMember us-gaap:LondonInterbankOfferedRateLIBORMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:DesignatedAsHedgingInstrumentMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:KingsbridgeMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-04-01 2020-06-30 0000776867 wtm:OtherOperationsMember wtm:TermLoanMember 2020-06-30 0000776867 wtm:KuduMember srt:MaximumMember wtm:KuduBankFacilityMember us-gaap:LineOfCreditMember us-gaap:PrimeRateMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-04-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2020-03-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember wtm:TermLoanMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2018-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:RevolvingCreditFacilityMember 2020-04-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember 2019-03-31 0000776867 wtm:BamMember us-gaap:SegmentContinuingOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:BamMember us-gaap:SegmentContinuingOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateCapMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2019-01-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2018-06-15 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2020-04-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateCapMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2020-01-01 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember currency:USD wtm:NSMBankFacilityMember us-gaap:InterestRateCapMember 2020-06-04 0000776867 wtm:NSMInsuranceGroupMember us-gaap:InterestRateSwapMember 2019-04-01 2019-06-30 0000776867 wtm:NSMInsuranceGroupMember currency:GBP wtm:NSMBankFacilityMember us-gaap:InterestRateCapMember 2020-06-04 0000776867 wtm:BamMember 2019-01-01 2019-12-31 0000776867 wtm:BamMember 2019-12-31 0000776867 wtm:BamMember 2020-06-30 0000776867 wtm:BamMember 2020-01-01 2020-06-30 0000776867 wtm:BamMember wtm:FidusReLtd.Member 2018-04-30 0000776867 wtm:BamMember wtm:SupplementalTrustMember 2020-01-01 2020-03-31 0000776867 wtm:BamMember wtm:FidusReLtd.Member 2018-10-01 2018-12-31 0000776867 wtm:HgGlobalMember 2020-06-30 0000776867 wtm:BamMember 2018-01-01 2018-12-31 0000776867 wtm:BamMember wtm:FidusReLtd.Member 2018-12-31 0000776867 wtm:BamMember wtm:SurplusNoteMember wtm:CombinationOneMember 2018-01-01 2018-03-31 0000776867 wtm:BamManagementMember 2012-01-01 2012-12-31 0000776867 wtm:HgGlobalMember 2019-12-31 0000776867 wtm:BamMember 2020-06-30 0000776867 wtm:BamMember srt:ScenarioForecastMember wtm:SurplusNoteMember wtm:FixedinterestrateMember 2024-12-31 0000776867 wtm:FidusReLtd.Member wtm:BamMember 2018-04-01 2018-04-30 0000776867 wtm:BamMember wtm:SurplusNoteMember wtm:FixedinterestrateMember 2018-12-31 0000776867 wtm:HgReMember 2020-01-01 2020-06-30 0000776867 wtm:HgGlobalMember wtm:SeriesABAMSurplusNoteMember 2017-12-31 0000776867 wtm:BamMember 2020-03-31 0000776867 wtm:BamMember 2018-01-01 2018-03-31 0000776867 wtm:HgGlobalMember us-gaap:CommonStockMember 2020-03-31 0000776867 wtm:HgGlobalMember 2020-01-01 2020-06-30 0000776867 wtm:BamMember 2019-12-31 0000776867 wtm:BamMember wtm:SurplusNoteMember 2020-01-01 2020-03-31 0000776867 wtm:BamMember wtm:SurplusNoteMember 2019-12-31 0000776867 wtm:BamMember wtm:FidusReLtd.Member srt:MaximumMember 2018-04-30 0000776867 wtm:BamMember wtm:FidusReLtd.Member 2018-04-01 2018-04-30 0000776867 wtm:BamMember wtm:SurplusNoteMember 2020-03-31 0000776867 wtm:HgGlobalMember wtm:BamMember 2020-01-01 2020-01-31 0000776867 wtm:HgGlobalMember 2012-01-01 2012-12-31 0000776867 wtm:BamMember srt:ScenarioForecastMember wtm:SurplusNoteMember 2020-12-31 0000776867 wtm:BamMember 2019-09-30 0000776867 wtm:BamMember wtm:SupplementalTrustMember 2020-03-31 0000776867 wtm:HgGlobalMember wtm:BamMember srt:MaximumMember 2020-01-31 0000776867 wtm:HGBAMMember 2020-01-01 2020-06-30 0000776867 wtm:HGBAMMember 2019-04-01 2019-06-30 0000776867 wtm:HGBAMMember 2020-04-01 2020-06-30 0000776867 wtm:HGBAMMember 2019-01-01 2019-06-30 0000776867 wtm:BamMember wtm:FirstQuarteryeartwoMember 2020-06-30 0000776867 wtm:BamMember wtm:FourthQuarteryeartwoMember 2020-06-30 0000776867 wtm:BamMember wtm:SecondQuarteryeartwoMember 2020-06-30 0000776867 wtm:BamMember wtm:ThirdQuarteryeartwoMember 2020-06-30 0000776867 wtm:BamMember wtm:SurplusNoteMember wtm:USTreasuryRateMember 2020-01-01 2020-06-30 0000776867 wtm:BamMember wtm:FidusReLtd.Member 2020-01-01 2020-03-31 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2019-04-01 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2019-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2020-04-01 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2019-03-31 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2019-01-01 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2020-01-01 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2018-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:RestrictedStockMember wtm:WTMIncentivePlanMember 2020-03-31 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember wtm:PerformanceCycle2019to2021Member 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember wtm:PerformanceCycle2018to2020Member 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember wtm:RangeOfPerformanceCycleFrom20172019Member 2020-06-30 0000776867 wtm:WhiteMountainsMember wtm:RestrictedShareCliffVestinginJanuary2022Member wtm:WTMIncentivePlanMember 2019-01-01 2019-06-30 0000776867 us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember wtm:RangeOfPerformanceCycleFrom20172019Member 2020-01-01 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2019-01-01 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember 2020-01-01 2020-06-30 0000776867 wtm:WhiteMountainsMember wtm:RestrictedShareCliffVestinginJanuary2022Member wtm:WTMIncentivePlanMember 2019-04-01 2019-06-30 0000776867 us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember wtm:RangeOfPerformanceCycleFrom20162018Member 2019-01-01 2019-06-30 0000776867 wtm:WhiteMountainsMember wtm:RestrictedShareCliffVestinginJanuary2023Member wtm:WTMIncentivePlanMember 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2019-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2020-04-01 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2020-01-01 2020-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2019-04-01 2019-06-30 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2020-03-31 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2018-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2019-03-31 0000776867 wtm:WhiteMountainsMember us-gaap:PerformanceSharesMember wtm:WTMIncentivePlanMember 2020-01-01 2020-03-31 0000776867 us-gaap:AccountingStandardsUpdate201602Member 2019-12-31 0000776867 wtm:OtherMember 2020-06-30 0000776867 wtm:HGBAMMember 2020-06-30 0000776867 wtm:HGBAMMember 2019-12-31 0000776867 wtm:OtherMember 2019-12-31 0000776867 wtm:OtherOperationsMember 2019-12-31 0000776867 wtm:TotalNonControllingExcludingReciprocalsMember 2020-06-30 0000776867 wtm:HgGlobalMember 2020-06-30 0000776867 wtm:HgGlobalMember 2019-12-31 0000776867 wtm:TotalNonControllingExcludingReciprocalsMember 2019-12-31 0000776867 wtm:OtherNSMMember 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2019-12-31 0000776867 wtm:BuildAmericaMutualMember 2019-12-31 0000776867 wtm:BuildAmericaMutualMember 2020-06-30 0000776867 wtm:OtherOperationsMember 2020-06-30 0000776867 wtm:KuduInvestmentManagementLLCMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember 2020-06-30 0000776867 wtm:OtherNSMMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember 2019-12-31 0000776867 wtm:CommissionandOtherRevenueMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 country:GB 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 country:GB wtm:KuduMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember 2019-01-01 2019-06-30 0000776867 wtm:KuduMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 country:GB wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember 2019-01-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 country:GB wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 wtm:OtherMember 2019-01-01 2019-06-30 0000776867 wtm:SocialServicesMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:OtherOperationsMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 wtm:PetMember wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 country:GB wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:KuduMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:HgGlobalBamMember 2019-01-01 2019-06-30 0000776867 country:GB wtm:NSMInsuranceGroupMember 2019-01-01 2019-06-30 0000776867 us-gaap:AdvertisingMember wtm:MediaAlphaMember 2019-01-01 2019-06-30 0000776867 us-gaap:ProductMember 2019-01-01 2019-06-30 0000776867 wtm:TotalMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember 2019-04-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:KuduMember 2019-04-01 2019-06-30 0000776867 wtm:OtherMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:OtherMember 2019-04-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember 2019-04-01 2019-06-30 0000776867 country:GB wtm:KuduMember 2019-04-01 2019-06-30 0000776867 wtm:PetMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 us-gaap:ProductMember 2019-04-01 2019-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:PetMember 2019-04-01 2019-06-30 0000776867 wtm:PetMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 country:GB wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 us-gaap:RealEstateMember 2019-04-01 2019-06-30 0000776867 country:GB 2019-04-01 2019-06-30 0000776867 country:GB wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:OtherMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 country:GB wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:SocialServicesMember 2019-04-01 2019-06-30 0000776867 wtm:PetMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:NSMInsuranceGroupMember 2019-04-01 2019-06-30 0000776867 us-gaap:RealEstateMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 wtm:SocialServicesMember wtm:OtherOperationsMember 2019-04-01 2019-06-30 0000776867 wtm:OtherMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:KuduMember 2019-04-01 2019-06-30 0000776867 us-gaap:ProductMember wtm:HgGlobalBamMember 2019-04-01 2019-06-30 0000776867 wtm:TotalMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2020-01-01 2020-06-30 0000776867 srt:AffiliatedEntityMember 2020-01-01 2020-06-30 0000776867 us-gaap:SegmentDiscontinuedOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:TotalMember 2019-01-01 2019-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:PetMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 us-gaap:ProductMember 2020-01-01 2020-06-30 0000776867 wtm:SocialServicesMember 2020-01-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember 2020-01-01 2020-06-30 0000776867 country:GB wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 country:GB 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:PetMember 2020-01-01 2020-06-30 0000776867 wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 us-gaap:RealEstateMember 2020-01-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:PetMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 wtm:PetMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:OtherMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 country:GB wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 country:GB wtm:KuduMember 2020-01-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:OtherOperationsMember 2020-01-01 2020-06-30 0000776867 wtm:PetMember wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:NSMInsuranceGroupMember 2020-01-01 2020-06-30 0000776867 country:GB wtm:HgGlobalBamMember 2020-01-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:KuduMember 2020-01-01 2020-06-30 0000776867 wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 us-gaap:ProductMember 2020-04-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:OtherMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 wtm:SocialServicesMember 2020-04-01 2020-06-30 0000776867 wtm:OtherMember 2020-04-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 country:GB wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 wtm:PetMember 2020-04-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:OtherMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 country:GB wtm:KuduMember 2020-04-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:OtherMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 us-gaap:RealEstateMember 2020-04-01 2020-06-30 0000776867 country:GB 2020-04-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 country:GB wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember 2020-04-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember wtm:KuduMember 2020-04-01 2020-06-30 0000776867 us-gaap:RealEstateMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 country:GB wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:CommissionandOtherRevenueMember 2020-04-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:HgGlobalBamMember 2020-04-01 2020-06-30 0000776867 wtm:SpecialtyTransportationMember wtm:OtherOperationsMember 2020-04-01 2020-06-30 0000776867 wtm:SocialServicesMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:OtherMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 us-gaap:ProductMember wtm:NSMInsuranceGroupMember 2020-04-01 2020-06-30 0000776867 wtm:TotalMember 2019-04-01 2019-06-30 0000776867 wtm:MediaAlphaMember 2019-03-31 0000776867 wtm:MediaAlphaMember 2019-02-26 2019-03-31 0000776867 wtm:MediaAlphaMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-01-01 2019-12-31 0000776867 wtm:MediaAlphaMember 2020-04-01 2020-06-30 0000776867 wtm:PassportDavidShieldMember 2020-04-01 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2019-01-01 2019-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2020-01-01 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2020-04-01 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2019-04-01 2019-06-30 0000776867 wtm:WhiteMountainsMember wtm:LimitedliabilitycompaniesandprivateequitysecuritiesMember 2020-06-30 0000776867 wtm:WhiteMountainsMember wtm:LimitedliabilitycompaniesandprivateequitysecuritiesMember 2019-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:OtherInvestmentsMember 2019-12-31 0000776867 wtm:WhiteMountainsMember us-gaap:OtherInvestmentsMember 2020-06-30 0000776867 wtm:ElementumHoldingsL.P.Member 2019-12-31 0000776867 wtm:MediaAlphaMember 2020-06-30 0000776867 wtm:MediaAlphaMember 2019-12-31 0000776867 wtm:JAMPartnersL.P.Member 2019-12-31 0000776867 wtm:ElementumHoldingsL.P.Member 2020-06-30 0000776867 wtm:DurchblickerMember 2019-12-31 0000776867 wtm:DurchblickerMember 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2020-06-30 0000776867 wtm:MediaAlphaKuduandTuckermanMember 2019-12-31 0000776867 srt:MaximumMember wtm:EnlightenmentCapitalFundsMember 2019-12-31 0000776867 srt:MaximumMember wtm:KuduInvestmentsMember 2019-12-31 0000776867 srt:MinimumMember wtm:TuckermanCapitalFundIIIL.P.Member 2020-06-30 0000776867 srt:MaximumMember wtm:TuckermanCapitalFundIIIL.P.Member 2020-06-30 0000776867 srt:MaximumMember wtm:EnlightenmentCapitalFundsMember 2020-06-30 0000776867 srt:MaximumMember wtm:TuckermanCapitalFundIIIL.P.Member 2019-12-31 0000776867 srt:MaximumMember wtm:KuduInvestmentsMember 2020-06-30 0000776867 srt:MinimumMember wtm:EnlightenmentCapitalFundsMember 2020-06-30 0000776867 srt:MinimumMember wtm:KuduInvestmentsMember 2020-06-30 0000776867 srt:MinimumMember wtm:TuckermanCapitalFundIIIL.P.Member 2019-12-31 0000776867 srt:MinimumMember wtm:EnlightenmentCapitalFundsMember 2019-12-31 0000776867 srt:MinimumMember wtm:KuduInvestmentsMember 2019-12-31 0000776867 wtm:KuduMember wtm:KuduDebtMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:CarryingReportedAmountFairValueDisclosureMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:CarryingReportedAmountFairValueDisclosureMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:OtherNSMMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2019-12-31 0000776867 wtm:KuduMember wtm:KuduDebtMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2020-06-30 0000776867 wtm:OtherOperationsMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2020-06-30 0000776867 wtm:OtherOperationsMember us-gaap:CarryingReportedAmountFairValueDisclosureMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2020-06-30 0000776867 wtm:OtherOperationsMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2019-12-31 0000776867 wtm:NSMInsuranceGroupMember wtm:OtherNSMMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2020-06-30 0000776867 wtm:NSMInsuranceGroupMember wtm:NSMBankFacilityMember us-gaap:EstimateOfFairValueFairValueDisclosureMember 2019-12-31 0000776867 wtm:SiriusGroupMember wtm:SiriusGroupMember wtm:SwedishTaxAuthorityMember 2020-04-01 2020-06-30 0000776867 wtm:SiriusGroupMember wtm:SiriusGroupMember wtm:SwedishTaxAuthorityMember 2019-12-31 0000776867 wtm:SiriusGroupMember wtm:SiriusGroupMember wtm:SwedishTaxAuthorityMember 2020-06-30 0000776867 stpr:CT us-gaap:DiscontinuedOperationsHeldforsaleMember 2019-12-31 0000776867 us-gaap:SegmentDiscontinuedOperationsMember 2019-04-01 2019-06-30 0000776867 us-gaap:SegmentDiscontinuedOperationsMember 2019-01-01 2019-06-30 0000776867 us-gaap:SegmentDiscontinuedOperationsMember 2020-04-01 2020-06-30 0000776867 stpr:CT us-gaap:DiscontinuedOperationsHeldforsaleMember 2020-06-30 wtm:earnout_period iso4217:USD iso4217:USD xbrli:shares xbrli:pure xbrli:shares wtm:Investment wtm:fund utreg:Y wtm:Contract wtm:multiplier
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
 
FORM 10-Q
    QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
 
For the period ended June 30, 2020
 
OR
 
         TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
 
For the transition period from          to         
Commission file number 1-8993

WHITE MOUNTAINS INSURANCE GROUP, LTD.
(Exact name of Registrant as specified in its charter)
Bermuda
 

(State or other jurisdiction of incorporation or organization)
 
94-2708455
23 South Main Street, Suite 3B
 
(I.R.S. Employer Identification No.)
Hanover,
 
03755-2053
New Hampshire
 
(Zip Code)
(Address of principal executive offices)
 
 
 
Registrant’s telephone number, including area code: (603640-2200
 Securities registered pursuant to Section 12(b) of the Act:
Title of each class
 
Trading Symbol(s)
 
Name of each exchange on which registered
Common Shares, par value $1.00
 
WTM
 
New York Stock Exchange
per share
 
 
 
Bermuda Stock Exchange
Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes   ý   No   
 
Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes       No   
 
Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company.  See the definitions of “large accelerated filer,” “accelerated filer”, “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.
Large accelerated filer
ý
Accelerated filer
Non-accelerated filer
Smaller reporting company
Emerging growth company
 

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  o
 
Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes     No  ý

As of August 5, 2020, 3,101,761 common shares with a par value of $1.00 per share were outstanding (which includes 43,105 restricted common shares that were not vested at such date).




WHITE MOUNTAINS INSURANCE GROUP, LTD.

Table of Contents
 
 
 
Page No.
 
 
 
 
 
 
 
 
 
 
 
 
Consolidated Balance Sheets, June 30, 2020 and December 31, 2019
 
 
 
 
 
 
     Three and Six Months Ended June 30, 2020 and 2019
 
 
 
 
Consolidated Statements of Changes in Equity,
 
     Three and Six Months Ended June 30, 2020 and 2019
 
 
 
 
 
Consolidated Statements of Cash Flows, Six Months Ended June 30, 2020 and 2019
<