XML 71 R68.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Derivatives (Variable Annuity Reinsurance Liabilities and Derivative Instruments (Details) (White Mountains Life Re, USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2014 | Mar. 31, 2013
Changes in derivative instruments |  |
Beginning balance | $ 69.2 |
Realized and unrealized gains (losses) | (6.6) | (181.8)
Ending balance | 89.6 |
Change in fair value of variable annuity death benefit liabilities, included in other general and administrative expenses | 0 | (5.6)
Fair Value |  |
Changes in derivative instruments |  |
Purchases | 0 |
Beginning balance | 69.2 | 98.3
Purchases |  | 36.1
Realized and unrealized gains (losses) | 6.6 | 181.8
Transfers in | 0 | 0
Sales/settlements | 27.0 | 123.2
Ending balance | 89.6 | 75.8
Level 3 Inputs |  |
Changes in derivative instruments |  |
Beginning balance | (52.8) | (441.5)
Purchases | 0 | 0
Realized and unrealized gains (losses) | (1.3) | 189.9
Transfers in | 0 | 0
Sales/settlements | 0 | 0
Ending balance | (54.1) | (251.6)
Beginning balance | 63.4 | 140.5
Purchases |  | 36.1
Realized and unrealized gains (losses) | 0.7 | (49.2)
Transfers in | 0 | 0
Sales/settlements | 0 | 0
Ending balance | 64.1 | 127.4
Level 2 Inputs |  |
Changes in derivative instruments |  |
Purchases | 0 |
Beginning balance | 4.7 | (20.5)
Purchases |  | 0
Realized and unrealized gains (losses) | 7.1 | 85.5
Transfers in | 0 | 0
Sales/settlements | 27.5 | 63.1
Ending balance | 25.1 | (42.9)
Level 1 Inputs |  |
Changes in derivative instruments |  |
Purchases | 0 |
Beginning balance | 1.1 | (21.7)
Purchases |  | 0
Realized and unrealized gains (losses) | 0.2 | 47.1
Transfers in | 0 | 0
Sales/settlements | (0.5) | 60.1
Ending balance | $ 0.4 | $ (8.7)

X
- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13495-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 + Details
Name: | us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + 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 (c)(1) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + 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 (c) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | wtm_DerivativeInstrumentsRollForward
Namespace Prefix: | wtm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Derivative Transfers In (Out), Net + References No definition available. + Details
Name: | wtm_DerivativeTransfersInOutNet
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Purchases that have taken place during the period in relation to derivative assets measured at fair value on a recurring basis. + References No definition available. + Details
Name: | wtm_FairValueDerivativesMeasuredOnRecurringBasisAssetPurchases
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Sales and settlements that have taken place during the period in relation to derivative assets measured at fair value on a recurring basis. + References No definition available. + Details
Name: | wtm_FairValueDerivativesMeasuredOnRecurringBasisAssetSalesAndSettlements
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers + References No definition available. + Details
Name: | wtm_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfers
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Sales or settlements that have taken place during the period in relation to liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | wtm_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySalesOrSettlements
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Net increase or decrease in the fair value of the variable annuity death benefit liabilities included in earnings. + References No definition available. + Details
Name: | wtm_GainLossOnLiabilityForDeathBenefit
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration