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Derivatives (Uncollateralized Amounts Due Under WM Life Re's OTC Derivative Contracts) (Details) - White Mountains Life Re $ in Thousands | Dec. 31, 2015 USD ($) Rating
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Credit risk on derivative instruments |
Excess collateral provided - Financial Instruments | $ 20,100
Collertal provided to counterparty in cash | 0
Collateral provided to counterparty in financial instruments | 0
Net amount of exposure after effect of collateral | 20,100
Excess collateral provided to counterparty in cash | 5,800
Derivative, Collateral, Right to Reclaim Securities | 0
Counter-party collateral held by WMLife Re - Cash | 6,900
Net amount of exposure to counter-party | $ 19,000
S and P Credit Ratings | Rating | 23
Standard & Poor's, A Rating [Member] | Bank of America [Member] |
Credit risk on derivative instruments |
Excess collateral provided - Financial Instruments | $ 700
Collertal provided to counterparty in cash | 0
Collateral provided to counterparty in financial instruments | 0
Net amount of exposure after effect of collateral | 700
Excess collateral provided to counterparty in cash | 0
Derivative, Collateral, Right to Reclaim Securities | 0
Counter-party collateral held by WMLife Re - Cash | 0
Net amount of exposure to counter-party | 700
Standard & Poor's, A Rating [Member] | Citigroup - OTC |
Credit risk on derivative instruments |
Excess collateral provided - Financial Instruments | 9,900
Collertal provided to counterparty in cash | 0
Collateral provided to counterparty in financial instruments | 0
Net amount of exposure after effect of collateral | 9,900
Excess collateral provided to counterparty in cash | 0
Derivative, Collateral, Right to Reclaim Securities | 0
Counter-party collateral held by WMLife Re - Cash | 1,400
Net amount of exposure to counter-party | 8,500
Standard & Poor's, A Rating [Member] | Citigroup Exchange Traded [Member] |
Credit risk on derivative instruments |
Excess collateral provided - Financial Instruments | 1,000
Collertal provided to counterparty in cash | 0
Collateral provided to counterparty in financial instruments | 0
Net amount of exposure after effect of collateral | 1,000
Excess collateral provided to counterparty in cash | 5,800
Derivative, Collateral, Right to Reclaim Securities | 0
Counter-party collateral held by WMLife Re - Cash | 0
Net amount of exposure to counter-party | 6,800
Standard & Poor's, A plus | JP Morgan |
Credit risk on derivative instruments |
Excess collateral provided - Financial Instruments | 8,500
Collertal provided to counterparty in cash | 0
Collateral provided to counterparty in financial instruments | 0
Net amount of exposure after effect of collateral | 8,500
Excess collateral provided to counterparty in cash | 0
Derivative, Collateral, Right to Reclaim Securities | 0
Counter-party collateral held by WMLife Re - Cash | 5,500
Net amount of exposure to counter-party | $ 3,000

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