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v2.4.1.9

Derivatives Forward Contracts (Details) In Millions, unless otherwise specified |  |  | 3 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2015 USD ($) | Mar. 31, 2015 JPY (¥) | Dec. 31, 2014 USD ($) | Dec. 31, 2014 JPY (¥) | Mar. 31, 2015 Forward Contracts USD ($) | Mar. 31, 2014 Forward Contracts USD ($) | Mar. 31, 2015 Forward Contracts SEK | Dec. 31, 2014 Forward Contracts USD ($)
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |  |  |
Notional amount | $ 1,000.0 invest_DerivativeNotionalAmount | ¥ 117,800.0 invest_DerivativeNotionalAmount | $ 1,100.0 invest_DerivativeNotionalAmount | ¥ 134,200.0 invest_DerivativeNotionalAmount | $ 56.5 invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  | 489.3 invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember | $ 33.1 invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember
Realized and unrealized gains (losses) |  |  |  |  | 0 us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember | (0.1)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |
Carrying Value |  |  |  |  | $ 0 wtm_UncollaterailizedBalanceOfForwardCurrencyDerivatives / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  | $ 0 wtm_UncollaterailizedBalanceOfForwardCurrencyDerivatives / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- 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
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- Details
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- Definition Uncollaterailized Balance of Forward Currency Derivatives + References No definition available. + Details
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