XML 29 R47.htm IDEA: XBRL DOCUMENT v2.4.1.9
Investments - Contractual maturities of available for sale securities (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Fixed Maturities - AFS    
Amortized cost of fixed maturities $ 27,370,101us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis $ 27,728,771us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Fixed maturities, at fair value 29,110,400us-gaap_AvailableForSaleSecuritiesDebtSecurities 29,359,034us-gaap_AvailableForSaleSecuritiesDebtSecurities
Trading Securities, Debt, Amortized Cost 138,647us-gaap_TradingSecuritiesDebtAmortizedCost 1,180us-gaap_TradingSecuritiesDebtAmortizedCost
Trading Securities Debt Maturities And Short Term Investments 139,377us-gaap_TradingSecuritiesDebt 1,171us-gaap_TradingSecuritiesDebt
Excluding Life Funds Withheld Assets    
Fixed Maturities - AFS    
Due less than one year, amortized cost 1,770,647us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 1,972,224us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due less than one year, fair value 1,781,224us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 1,980,429us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 1 through 5 years, amortized cost 9,698,659us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 8,919,037us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 1 through 5 years, fair value 9,923,517us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 9,113,651us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 5 through 10 years, amortized cost 4,049,907us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 4,232,396us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 5 through 10 years, fair value 4,226,001us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 4,412,569us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 10 years, amortized cost 1,440,069us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 1,494,315us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Due after 10 years, fair value 1,669,149us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 1,705,022us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Subtotal - amortized cost 16,959,282us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 16,617,972us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Subtotal - fair value 17,599,891us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 17,211,671us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Mortgage and asset backed securities - amortized cost 6,620,330us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 6,809,460us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Mortgage and asset backed securities - fair value 6,792,530us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 6,965,798us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Amortized cost of fixed maturities 23,579,612us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 23,427,432us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Fixed maturities, at fair value 24,392,421us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember		 24,177,469us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
Excluding Life Funds Withheld Assets | RMBS - Agency    
Fixed Maturities - AFS    
Mortgage and asset backed securities - amortized cost 3,585,638us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 3,625,171us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Mortgage and asset backed securities - fair value 3,711,334us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 3,728,576us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Amortized cost of fixed maturities 3,585,638us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 3,625,171us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fixed maturities, at fair value 3,711,334us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 3,728,576us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Excluding Life Funds Withheld Assets | RMBS - Non-Agency    
Fixed Maturities - AFS    
Mortgage and asset backed securities - amortized cost 368,317us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 404,398us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Mortgage and asset backed securities - fair value 380,135us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 427,351us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Amortized cost of fixed maturities 368,317us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 404,398us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Fixed maturities, at fair value 380,135us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 427,351us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Excluding Life Funds Withheld Assets | Commercial mortgage-backed securities    
Fixed Maturities - AFS    
Mortgage and asset backed securities - amortized cost 1,010,518us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 1,033,819us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Mortgage and asset backed securities - fair value 1,032,720us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 1,052,544us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Amortized cost of fixed maturities 1,010,518us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 1,033,819us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Fixed maturities, at fair value 1,032,720us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 1,052,544us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Excluding Life Funds Withheld Assets | Collateralized debt obligations    
Fixed Maturities - AFS    
Mortgage and asset backed securities - amortized cost 520,929us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember		 717,544us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Mortgage and asset backed securities - fair value 500,974us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember		 692,034us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Amortized cost of fixed maturities 520,929us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember		 717,544us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Fixed maturities, at fair value 500,974us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember		 692,034us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CollateralizedDebtObligationsMember
Excluding Life Funds Withheld Assets | Other asset-backed securities    
Fixed Maturities - AFS    
Mortgage and asset backed securities - amortized cost 1,134,928us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 1,028,528us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Mortgage and asset backed securities - fair value 1,167,367us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 1,065,293us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Amortized cost of fixed maturities 1,134,928us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 1,028,528us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Fixed maturities, at fair value 1,167,367us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember		 1,065,293us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_ExcludeLifeFundsWithheldAssetsMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Life Funds Withheld Assets    
Fixed Maturities - AFS    
Due less than one year, amortized cost 97,637us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 117,048us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due less than one year, fair value 107,530us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 125,326us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 1 through 5 years, amortized cost 626,869us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 638,526us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 1 through 5 years, fair value 676,507us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 685,787us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 5 through 10 years, amortized cost 798,923us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 1,004,698us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 5 through 10 years, fair value 933,986us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 1,165,348us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 10 years, amortized cost 1,890,995us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 2,059,637us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Due after 10 years, fair value 2,555,621us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 2,649,279us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Subtotal - amortized cost 3,414,424us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 3,819,909us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Subtotal - fair value 4,273,644us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 4,625,740us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Mortgage and asset backed securities - amortized cost 376,065us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 481,430us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Mortgage and asset backed securities - fair value 444,335us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 555,825us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Amortized cost of fixed maturities 3,790,489us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 4,301,339us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Fixed maturities, at fair value 4,717,979us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 5,181,565us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Trading Securities, Debt, Amortized Cost 138,647us-gaap_TradingSecuritiesDebtAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 1,180us-gaap_TradingSecuritiesDebtAmortizedCost
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
Trading Securities Debt Maturities And Short Term Investments 139,377us-gaap_TradingSecuritiesDebt
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember		 1,171us-gaap_TradingSecuritiesDebt
/ us-gaap_InvestmentTypeAxis
= xlgroup_LifeFundsWithheldAssetsMember
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Fixed Maturities - AFS    
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Life Funds Withheld Assets | Fair value    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | RMBS - Agency    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | RMBS - Non-Agency    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | Commercial mortgage-backed securities    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | Other asset-backed securities    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | Other asset-backed securities | Cost    
Fixed Maturities - AFS    
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Life Funds Withheld Assets | Other asset-backed securities | Fair value    
Fixed Maturities - AFS    
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