Fair Value (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 13,619,948		$ 13,619,948		$ 13,941,829
Short-term investments, trading securities, at fair value	31,984		31,984		42,571
Equities, trading securities	1,050,017		1,050,017		944,691
Other invested assets	53,972		53,972		90,512
Funds held - directly managed	1,088,800		1,088,800		1,057,553
Total	15,844,721		15,844,721		16,077,156
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	15,317	105,297	125,574	(31,075)
[FixedMaturitiesAndShortTermInvestmentsMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	32,995	131,101	80,815	(9,767)
[OtherInvestedAssetsMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	13,610	(3,689)	18,160	(3,333)
[EquitySecuritiesMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	(32,963)	(30,197)	17,808	(14,079)
[FundsHeldDirectlyManagedInvestmentMember]
Fair Value, Option, Quantitative Disclosures [Line Items]
Change in unrealized gain/loss	1,675	8,082	8,791	(3,896)
[OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	72,529		72,529		91,405
[ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	10,546		10,546		18,097
[OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,076		15,076		15,433
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	2,483		2,483		7,865
[DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	182		182		1,074
[DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,819		1,819		13,572
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	22		22		92
[DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	324		324		246
[DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	261		261
[DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,115		7,115		7,673
[DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	674		674		747
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,683)		(5,683)		(5,816)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(2,021)		(2,021)		(321)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(8,149)		(8,149)		(14,173)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,142)		(1,142)		(1,285)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(79)		(79)		(772)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,423)		(5,423)		(968)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(746)		(746)		(640)
[DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(8,194)		(8,194)		(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	130,545		130,545		124,851
[FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	97,864		97,864		79,583
[TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	86,571		86,571		74,729
[EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	76,620		76,620		84,261
[InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	61,521		61,521		58,017
[CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	62,599		62,599		64,080
[IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	59,565		59,565		58,254
[ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	54,851		54,851		52,413
[OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	82,687		82,687		69,696
[MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	337,194		337,194		278,807
[USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	944,080		944,080		1,115,777
Funds held - directly managed	367,515		367,515		268,539
[USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	127,470		127,470		123,684
Funds held - directly managed	321		321		334
[NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,650,832		2,650,832		2,964,091
Funds held - directly managed	276,288		276,288		274,665
[CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	5,812,560		5,812,560		5,746,997
Funds held - directly managed	419,054		419,054		480,485
[AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	672,989		672,989		633,799
[ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,337,721		3,337,721		3,282,901
[CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	74,296		74,296		74,580
[FairValueInputsLevel1Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Short-term investments, trading securities, at fair value	0		0		0
Equities, trading securities	771,682		771,682		689,905
Other invested assets	(8,078)		(8,078)		619
Funds held - directly managed	0		0		0
Total	763,604		763,604		690,524
[FairValueInputsLevel1Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	71		71		13,524
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(8,149)		(8,149)		(12,905)
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel1Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		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	130,545		130,545		124,697
[FairValueInputsLevel1Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	78,442		78,442		69,722
[FairValueInputsLevel1Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	79,379		79,379		74,729
[FairValueInputsLevel1Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	76,620		76,620		83,403
[FairValueInputsLevel1Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	61,521		61,521		58,017
[FairValueInputsLevel1Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	62,599		62,599		64,036
[FairValueInputsLevel1Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	59,565		59,565		58,254
[FairValueInputsLevel1Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	54,851		54,851		52,305
[FairValueInputsLevel1Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	82,687		82,687		69,457
[FairValueInputsLevel1Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	85,473		85,473		35,285
[FairValueInputsLevel1Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel1Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
[FairValueInputsLevel1Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
[FairValueInputsLevel1Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
[FairValueInputsLevel2Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	13,101,272		13,101,272		13,461,299
Short-term investments, trading securities, at fair value	31,984		31,984		42,571
Equities, trading securities	244,961		244,961		238,621
Other invested assets	(11,686)		(11,686)		(7,134)
Funds held - directly managed	1,073,403		1,073,403		1,041,786
Total	14,439,934		14,439,934		14,777,143
[FairValueInputsLevel2Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel2Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	10,546		10,546		18,097
[FairValueInputsLevel2Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0		0		0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	2,483		2,483		7,865
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	182		182		1,074
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	1,748		1,748		48
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	22		22		92
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	324		324		246
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		443
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	674		674		747
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,683)		(5,683)		(5,816)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(2,021)		(2,021)		(321)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		(1,268)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(1,142)		(1,142)		(1,285)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(79)		(79)		(772)
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel2Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(8,194)		(8,194)		(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		0		154
[FairValueInputsLevel2Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		191
[FairValueInputsLevel2Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel2Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		858
[FairValueInputsLevel2Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel2Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		44
[FairValueInputsLevel2Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel2Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		108
[FairValueInputsLevel2Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		239
[FairValueInputsLevel2Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	244,961		244,961		237,027
[FairValueInputsLevel2Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	944,080		944,080		1,115,777
Funds held - directly managed	367,515		367,515		268,539
[FairValueInputsLevel2Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	10,235		10,235		12,269
Funds held - directly managed	0		0		0
[FairValueInputsLevel2Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	2,650,832		2,650,832		2,964,091
Funds held - directly managed	276,288		276,288		274,665
[FairValueInputsLevel2Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	5,701,490		5,701,490		5,635,297
Funds held - directly managed	419,054		419,054		480,485
[FairValueInputsLevel2Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	382,618		382,618		376,384
[FairValueInputsLevel2Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	3,337,721		3,337,721		3,282,901
[FairValueInputsLevel2Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	74,296		74,296		74,580
[FairValueInputsLevel3Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	518,676		518,676		480,530
Short-term investments, trading securities, at fair value	0		0		0
Equities, trading securities	33,374		33,374		16,165
Other invested assets	73,736		73,736		97,027
Funds held - directly managed	15,397		15,397		15,767
Total	641,183		641,183		609,489
[FairValueInputsLevel3Member] | [OtherInvestedAssetsOtherAssetsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	72,529		72,529		91,405
[FairValueInputsLevel3Member] | [ShortTermInvestmentsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	0		0		0
[FairValueInputsLevel3Member] | [OtherInvestedAssetsFundsHeldDirectlyManagedMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Funds held - directly managed	15,076		15,076		15,433
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	261		261
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	7,115		7,115		7,230
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsAssetsMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeForwardMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ForeignExchangeOptionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [FutureMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapBuyingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [CreditDefaultSwapSellingProtectionMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InsuranceLinkedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(5,423)		(5,423)		(968)
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [TotalReturnSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	(746)		(746)		(640)
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [InterestRateSwapMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0		0		0
[FairValueInputsLevel3Member] | [DerivativeFinancialInstrumentsLiabilitiesMember] | [ToBeAnnouncedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets					0
[FairValueInputsLevel3Member] | [OtherInvestedAssetsOtherLiabilitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets					0
[FairValueInputsLevel3Member] | [ConsumerNoncyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [FinanceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	19,422		19,422		9,670
[FairValueInputsLevel3Member] | [TechnologyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	7,192		7,192		0
[FairValueInputsLevel3Member] | [EnergyMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [InsuranceMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [CommunicationsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [IndustrialsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [ConsumerCyclicalMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [OtherEquitiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [MutualFundsAndExchangeTradedFundsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equities, trading securities	6,760		6,760		6,495
[FairValueInputsLevel3Member] | [USTreasuryAndGovernmentMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel3Member] | [USStatesAndPoliticalSubdivisionsMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	117,235		117,235		111,415
Funds held - directly managed	321		321		334
[FairValueInputsLevel3Member] | [NonUsSovereignGovernmentSupranationalAndGovernmentRelatedDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
Funds held - directly managed	0		0		0
[FairValueInputsLevel3Member] | [CorporateDebtSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	111,070		111,070		111,700
Funds held - directly managed	0		0		0
[FairValueInputsLevel3Member] | [AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	290,371		290,371		257,415
[FairValueInputsLevel3Member] | [ResidentialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	0		0		0
[FairValueInputsLevel3Member] | [CommercialMortgageBackedSecuritiesMember]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, trading securities	$ 0		$ 0		$ 0