Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 14,338,499	$ 13,941,829
Short-term investments, trading securities, at fair value	161,137	42,571
Equities, trading securities	1,071,528	944,691
Other invested assets	66,432	90,512
Funds held - directly managed	1,061,349	1,057,553
Total	16,698,945	16,077,156
[OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	72,619	91,405
[ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		18,097
[OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	17,536	15,433
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	11,229	7,865
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,061	1,074
[DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		13,572
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	16	92
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	452	246
[DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	56
[DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	6,214	7,673
[DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,368	747
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,744)	(5,816)
[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	(11,462)	(14,173)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,071)	(1,285)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(772)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,290)	(968)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(621)	(640)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(8,395)	(7,992)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(58)
[OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(137)
[ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	127,963	124,851
[FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	102,057	79,583
[TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	84,125	74,729
[EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	118,502	84,261
[InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	64,983	58,017
[CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	69,182	64,080
[IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	56,220	58,254
[ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	55,453	52,413
[OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	84,492	69,696
[MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	308,551	278,807
[USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	982,433	1,115,777
Funds held - directly managed	356,444	268,539
[USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	219,089	123,684
Funds held - directly managed	329	334
[NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,638,242	2,964,091
Funds held - directly managed	272,585	274,665
[CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	6,377,855	5,746,997
Funds held - directly managed	414,455	480,485
[AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	722,688	633,799
[ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,319,929	3,282,901
[CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	78,263	74,580
[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	777,634	689,905
Other invested assets	(11,462)	619
Funds held - directly managed	0	0
Total	766,172	690,524
[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
[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
[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	0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	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	(11,462)	(12,905)
[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
[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
[FairValueInputsLevel1Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
[FairValueInputsLevel1Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	127,963	124,697
[FairValueInputsLevel1Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	81,100	69,722
[FairValueInputsLevel1Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	77,032	74,729
[FairValueInputsLevel1Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	118,502	83,403
[FairValueInputsLevel1Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	64,983	58,017
[FairValueInputsLevel1Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	69,182	64,036
[FairValueInputsLevel1Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	56,220	58,254
[FairValueInputsLevel1Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	55,453	52,305
[FairValueInputsLevel1Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	84,492	69,457
[FairValueInputsLevel1Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	42,707	35,285
[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] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
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	13,691,933	13,461,299
Short-term investments, trading securities, at fair value	161,137	42,571
Equities, trading securities	266,358	238,621
Other invested assets	916	(7,134)
Funds held - directly managed	1,043,484	1,041,786
Total	15,163,828	14,777,143
[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
[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	11,229	7,865
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,061	1,074
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		48
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	16	92
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	452	246
[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	443
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,368	747
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(3,744)	(5,816)
[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	0	(1,268)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,071)	(1,285)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(772)
[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	(8,395)	(7,992)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(58)
[FairValueInputsLevel2Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		(137)
[FairValueInputsLevel2Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	154
[FairValueInputsLevel2Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	7,585	191
[FairValueInputsLevel2Member] | [TechnologyMember]
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	858
[FairValueInputsLevel2Member] | [InsuranceMember]
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	44
[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	108
[FairValueInputsLevel2Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	239
[FairValueInputsLevel2Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	258,773	237,027
[FairValueInputsLevel2Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	982,433	1,115,777
Funds held - directly managed	356,444	268,539
[FairValueInputsLevel2Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	10,269	12,269
Funds held - directly managed	0	0
[FairValueInputsLevel2Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,638,242	2,964,091
Funds held - directly managed	272,585	274,665
[FairValueInputsLevel2Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	6,269,298	5,635,297
Funds held - directly managed	414,455	480,485
[FairValueInputsLevel2Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	393,499	376,384
[FairValueInputsLevel2Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,319,929	3,282,901
[FairValueInputsLevel2Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	78,263	74,580
[FairValueInputsLevel3Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	646,566	480,530
Short-term investments, trading securities, at fair value	0	0
Equities, trading securities	27,536	16,165
Other invested assets	76,978	97,027
Funds held - directly managed	17,865	15,767
Total	768,945	609,489
[FairValueInputsLevel3Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	72,619	91,405
[FairValueInputsLevel3Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed		0
[FairValueInputsLevel3Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	17,536	15,433
[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
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	56
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	6,214	7,230
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,290)	(968)
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(621)	(640)
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets		0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	13,372	9,670
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	7,093	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	7,071	6,495
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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
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	208,820	111,415
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0	0
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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