Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 13,379,611	$ 14,395,315
Short-term investments, trading securities, at fair value	29,379	150,552
Equities, trading securities	1,172,855	1,094,002
Other invested assets	144,877	71,204
Funds held - directly managed	670,199	833,247
Total	15,396,921	16,544,320
[ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	293
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,486	7,889
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		1,410
[DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	55,879	1,956
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		6
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	157	512
[DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	814
[DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	3,328	6,630
[DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	215
[DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1	115
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(4,656)	(17,395)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,280)	(186)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(9)	(1,352)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(404)	(807)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(906)	(2,173)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(903)	(546)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(4,919)	(7,880)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,805)	(163)
[OtherInvestedAssetsNotesAndLoanReceivablesAndNotesSecuritizationMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	44,224	34,902
[OtherInvestedAssetsAnnuitiesAndResidualsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	30,555	46,882
[PrivateEquitiesTotalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	21,100	1,404
[OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,207	17,976
[RealEstateInvestmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	173,606	66,846
[EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	161,676	118,213
[FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	136,021	100,405
[ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	126,009	130,526
[CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	74,322	65,722
[TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	63,376	78,914
[IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	47,066	59,242
[ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	44,455	62,526
[PublicUtilityEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	38,004
[InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	37,891	39,132
[OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	21,165	60,913
[MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	249,264	311,563
[USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	990,738	1,130,924
Funds held - directly managed	171,265	218,696
[USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	236,609	243,386
Funds held - directly managed	337	345
[NonUsSovereignGovernmentSupranationalAndGovernmentRelatedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,139,831	2,375,673
Funds held - directly managed	195,914	233,987
[CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	6,246,180	6,655,838
Funds held - directly managed	287,183	362,243
[AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	850,717	723,470
[ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,873,669	3,199,924
[CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	41,867	66,100
[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	928,577	788,556
Other invested assets	55,870	604
Funds held - directly managed	0	0
Total	984,447	789,160
[FairValueInputsLevel1Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	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
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	55,879	1,956
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		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	0
[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	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(9)	(1,352)
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
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	0
[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] | [OtherInvestedAssetsNotesAndLoanReceivablesAndNotesSecuritizationMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [OtherInvestedAssetsAnnuitiesAndResidualsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [PrivateEquitiesTotalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel1Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel1Member] | [RealEstateInvestmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	173,606	66,846
[FairValueInputsLevel1Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	161,676	118,213
[FairValueInputsLevel1Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	110,869	79,456
[FairValueInputsLevel1Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	126,009	130,526
[FairValueInputsLevel1Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	72,282	65,722
[FairValueInputsLevel1Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	55,364	71,927
[FairValueInputsLevel1Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	47,066	59,242
[FairValueInputsLevel1Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	44,455	62,526
[FairValueInputsLevel1Member] | [PublicUtilityEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	38,004
[FairValueInputsLevel1Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	37,891	39,132
[FairValueInputsLevel1Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	21,165	60,913
[FairValueInputsLevel1Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	40,190	34,053
[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] | [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	12,634,264	13,738,042
Short-term investments, trading securities, at fair value	29,379	150,552
Equities, trading securities	213,677	277,718
Other invested assets	(9,205)	(16,499)
Funds held - directly managed	654,655	814,926
Total	13,522,770	14,964,739
[FairValueInputsLevel2Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	293
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,486	7,889
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		1,410
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		6
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	157	512
[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	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	215
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1	115
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(4,656)	(17,395)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,280)	(186)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(404)	(807)
[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	(4,919)	(7,880)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,805)	(163)
[FairValueInputsLevel2Member] | [OtherInvestedAssetsNotesAndLoanReceivablesAndNotesSecuritizationMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [OtherInvestedAssetsAnnuitiesAndResidualsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [PrivateEquitiesTotalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
[FairValueInputsLevel2Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0	0
[FairValueInputsLevel2Member] | [RealEstateInvestmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	12,152	7,472
[FairValueInputsLevel2Member] | [ConsumerNoncyclicalMember]
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	0	0
[FairValueInputsLevel2Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [IndustrialsMember]
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	0	0
[FairValueInputsLevel2Member] | [PublicUtilityEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0
[FairValueInputsLevel2Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
[FairValueInputsLevel2Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	201,525	270,246
[FairValueInputsLevel2Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	990,738	1,130,924
Funds held - directly managed	171,265	218,696
[FairValueInputsLevel2Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	17,446	10,151
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	2,139,831	2,375,673
Funds held - directly managed	195,914	233,987
[FairValueInputsLevel2Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	6,146,284	6,554,934
Funds held - directly managed	287,183	362,243
[FairValueInputsLevel2Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	424,429	400,336
[FairValueInputsLevel2Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,873,669	3,199,924
[FairValueInputsLevel2Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	41,867	66,100
[FairValueInputsLevel3Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	745,347	657,273
Short-term investments, trading securities, at fair value	0	0
Equities, trading securities	30,601	27,728
Other invested assets	98,212	87,099
Funds held - directly managed	15,544	18,321
Total	889,704	790,421
[FairValueInputsLevel3Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0
[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
[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
[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	814
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	3,328	6,630
[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	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] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(906)	(2,173)
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(903)	(546)
[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] | [OtherInvestedAssetsNotesAndLoanReceivablesAndNotesSecuritizationMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	44,224	34,902
[FairValueInputsLevel3Member] | [OtherInvestedAssetsAnnuitiesAndResidualsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	30,555	46,882
[FairValueInputsLevel3Member] | [PrivateEquitiesTotalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	21,100	1,404
[FairValueInputsLevel3Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,207	17,976
[FairValueInputsLevel3Member] | [RealEstateInvestmentMember]
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	13,000	13,477
[FairValueInputsLevel3Member] | [ConsumerNoncyclicalMember]
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	2,040	0
[FairValueInputsLevel3Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	8,012	6,987
[FairValueInputsLevel3Member] | [IndustrialsMember]
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] | [PublicUtilityEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0
[FairValueInputsLevel3Member] | [InsuranceMember]
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	7,549	7,264
[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	219,163	233,235
Funds held - directly managed	337	345
[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	99,896	100,904
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	426,288	323,134
[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	$ 0