XML 30 R77.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Derivatives (Level 3 Derivative Instruments) (Details) (White Mountains Life Re, USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015
Discounted cash flows |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Fair value Liabilities | 1.1 us-gaap_LiabilitiesFairValueDisclosure / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember
Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Mortality (as a percent) | 0.00%wtm_FairValueInputsMortality / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember
Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Mortality (as a percent) | 6.40%wtm_FairValueInputsMortality / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember
Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Mortality (as a percent) | 1.00%wtm_FairValueInputsMortality / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember
Foreign Exchange Option [Member] | Counterparty valuations |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Fair value Liabilities | 11.1 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByLiabilityClassAxis = us-gaap_ForeignExchangeOptionMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Foreign Exchange Option [Member] | Counterparty valuations | Minimum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Foreign exchange volatilities (as a percent) | 0.50%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_ForeignExchangeOptionMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Foreign Exchange Option [Member] | Counterparty valuations | Maximum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Foreign exchange volatilities (as a percent) | 11.60%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_ForeignExchangeOptionMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Foreign Exchange Option [Member] | Counterparty valuations | Weighted Average |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Foreign exchange volatilities (as a percent) | 5.90%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_ForeignExchangeOptionMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Equity Index Options | Counterparty valuations |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Fair value Liabilities | 5.9 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByLiabilityClassAxis = wtm_EquityIndexOptionsMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Equity Index Options | Counterparty valuations | Minimum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Expected equity dividends (as a percent) | (0.70%)wtm_FairValueInputsSignificantUnobservableInputsForEquityIndexOptions / us-gaap_FairValueByLiabilityClassAxis = wtm_EquityIndexOptionsMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Equity Index Options | Counterparty valuations | Maximum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Expected equity dividends (as a percent) | 6.50%wtm_FairValueInputsSignificantUnobservableInputsForEquityIndexOptions / us-gaap_FairValueByLiabilityClassAxis = wtm_EquityIndexOptionsMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Equity Index Options | Counterparty valuations | Weighted Average |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Expected equity dividends (as a percent) | 2.10%wtm_FairValueInputsSignificantUnobservableInputsForEquityIndexOptions / us-gaap_FairValueByLiabilityClassAxis = wtm_EquityIndexOptionsMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_CounterpartyvaluationsMember
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 0.10%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Foreign exchange volatilities (as a percent) | 10.90%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Index volatilities (as a percent) | 24.80%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 40.00%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Foreign exchange volatilities (as a percent) | 16.20%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Index volatilities (as a percent) | 27.20%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Year One | Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 40.00%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Foreign exchange volatilities (as a percent) | 13.10%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Index volatilities (as a percent) | 26.70%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearOneMember
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Minimum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 0.20%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Foreign exchange volatilities (as a percent) | 10.90%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Index volatilities (as a percent) | 21.20%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Maximum |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 40.00%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Foreign exchange volatilities (as a percent) | 14.10%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Index volatilities (as a percent) | 23.90%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Year Two | Variable annuity benefit guarantee liabilities | Discounted cash flows | Weighted Average |
Quantitative information for Level 3 Fair Value Measurements Liabilities |
Surrenders (as a percent) | 32.20%wtm_FairValueInputsSurrenders / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Foreign exchange volatilities (as a percent) | 12.50%wtm_FairValueInputsForeignExchangeVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember
Index volatilities (as a percent) | 22.90%wtm_FairValueInputsIndexVolatilities / us-gaap_FairValueByLiabilityClassAxis = us-gaap_VariableAnnuityMember / dei_LegalEntityAxis = wtm_WhiteMountainsLifeReMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = wtm_DiscountedCashFlowValuationTechniqueMember / wtm_VolatilityYearAxis = wtm_YearTwoMember

X
- Details
Name: | us-gaap_FairValueInputsLiabilitiesQuantitativeInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the foreign exchange volatilities, used as an input to measure fair value. + References No definition available. + Details
Name: | wtm_FairValueInputsForeignExchangeVolatilities
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the index volatilities, used as an input to measure fair value. + References No definition available. + Details
Name: | wtm_FairValueInputsIndexVolatilities
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the mortality, used as an input to measure fair value. + References No definition available. + Details
Name: | wtm_FairValueInputsMortality
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Significant unobservable inputs for equity index options + References No definition available. + Details
Name: | wtm_FairValueInputsSignificantUnobservableInputsForEquityIndexOptions
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the surrenders, used as an input to measure fair value. + References No definition available. + Details
Name: | wtm_FairValueInputsSurrenders
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration