Fair Value (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 13,941,829	$ 12,824,389
Short-term investments, trading securities, at fair value	42,571	49,397
Equities, trading securities	944,691	1,071,676
Other invested assets	90,512	111,374
Funds held - directly managed	1,057,553	1,542,931
Total	16,077,156	15,599,767
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	7,378	230,641	512,807
[FixedMaturitiesAndShortTermInvestmentsMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	128,224	142,634	322,944
[OtherInvestedAssetsMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(24,839)	(1,176)	2,053
[EquitySecuritiesMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(101,860)	64,825	185,925
[FundsHeldDirectlyManagedInvestmentMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	5,853	24,358	1,885
[OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	91,405	86,278
[ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	18,097	38,613
[OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,433	20,528
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,865	27,880
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,074	3,516
[DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	13,572	30,593
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	92	93
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	246	533
[DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		1,320
[DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,673	6,041
[DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		246
[DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	747	363
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,816)	(13,647)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(321)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(14,173)	(7,956)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,285)	(2,407)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(772)	(401)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(968)	(1,393)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(640)	(12,848)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(7,992)	(6,033)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(58)	(553)
[OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(137)	(251)
[ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	124,851	186,016
[EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	84,261	118,372
[FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	79,583	114,795
[TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	74,729	119,214
[CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	64,080	110,982
[IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	58,254	100,572
[InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	58,017	48,611
[ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	52,413	81,595
[OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	69,696	90,220
[MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	278,807	101,299
[USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	1,115,777	906,032
Funds held - directly managed	268,539	288,164
[USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	123,684	66,692
Funds held - directly managed	334	368
[NonUsSovereignGovernmentSupranationalAndGovernmentRelatedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,964,091	2,819,193
Funds held - directly managed	274,665	384,553
[CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	5,746,997	6,143,847
Funds held - directly managed	480,485	798,587
[AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	633,799	556,657
[AssetBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		12,118
[ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,282,901	2,305,525
[CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	74,580	26,443
[FairValueInputsLevel1Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Short-term investments, trading securities, at fair value	0	0
Equities, trading securities	689,905	1,028,263
Other invested assets	619	23,262
Funds held - directly managed	0	0
Total	690,524	1,051,525
[FairValueInputsLevel1Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	13,524	30,593
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		1,320
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(12,905)	(7,956)
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	(695)
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	124,697	186,016
[FairValueInputsLevel1Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	83,403	118,372
[FairValueInputsLevel1Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	69,722	112,309
[FairValueInputsLevel1Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	74,729	119,214
[FairValueInputsLevel1Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	64,036	110,982
[FairValueInputsLevel1Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	58,254	100,572
[FairValueInputsLevel1Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	58,017	48,611
[FairValueInputsLevel1Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	52,305	81,595
[FairValueInputsLevel1Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	69,457	90,220
[FairValueInputsLevel1Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	35,285	60,372
[FairValueInputsLevel1Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
[FairValueInputsLevel1Member] | [AssetBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		0
[FairValueInputsLevel1Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
[FairValueInputsLevel1Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
[FairValueInputsLevel2Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	13,461,299	12,478,854
Short-term investments, trading securities, at fair value	42,571	49,397
Equities, trading securities	238,621	0
Other invested assets	(7,134)	9,788
Funds held - directly managed	1,041,786	1,509,917
Total	14,777,143	14,047,956
[FairValueInputsLevel2Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	18,097	38,613
[FairValueInputsLevel2Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,865	27,880
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,074	3,516
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	48	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	92	93
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	246	533
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	443	449
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		246
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	747	363
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,816)	(13,647)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(321)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,268)	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,285)	(2,407)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(772)	(401)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(7,992)	(6,033)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(58)	(553)
[FairValueInputsLevel2Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(137)	(251)
[FairValueInputsLevel2Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	154	0
[FairValueInputsLevel2Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	858	0
[FairValueInputsLevel2Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	191	0
[FairValueInputsLevel2Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	44	0
[FairValueInputsLevel2Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	108	0
[FairValueInputsLevel2Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	239	0
[FairValueInputsLevel2Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	237,027	0
[FairValueInputsLevel2Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	1,115,777	906,032
Funds held - directly managed	268,539	288,164
[FairValueInputsLevel2Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	12,269	11,568
Funds held - directly managed	0	0
[FairValueInputsLevel2Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,964,091	2,819,193
Funds held - directly managed	274,665	384,553
[FairValueInputsLevel2Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	5,635,297	6,066,865
Funds held - directly managed	480,485	798,587
[FairValueInputsLevel2Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	376,384	343,518
[FairValueInputsLevel2Member] | [AssetBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		0
[FairValueInputsLevel2Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,282,901	2,305,525
[FairValueInputsLevel2Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	74,580	26,153
[FairValueInputsLevel3Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	480,530	345,535
Short-term investments, trading securities, at fair value	0	0
Equities, trading securities	16,165	43,413
Other invested assets	97,027	78,324
Funds held - directly managed	15,767	33,014
Total	609,489	500,286
[FairValueInputsLevel3Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	91,405	86,278
[FairValueInputsLevel3Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel3Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,433	20,528
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,230	5,592
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(968)	(698)
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(640)	(12,848)
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel3Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	9,670	2,486
[FairValueInputsLevel3Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel3Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	6,495	40,927
[FairValueInputsLevel3Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel3Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	111,415	55,124
Funds held - directly managed	334	368
[FairValueInputsLevel3Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
Funds held - directly managed	0	0
[FairValueInputsLevel3Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	111,700	76,982
Funds held - directly managed	0	0
[FairValueInputsLevel3Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	257,415	213,139
[FairValueInputsLevel3Member] | [AssetBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		12,118
[FairValueInputsLevel3Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
[FairValueInputsLevel3Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 0	$ 290