v2.4.1.9
Summary of Aggregate Notional Amount and Fair Value of Derivative Financial Instruments (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional $ 443,088us-gaap_DerivativeAssetNotionalAmount $ 719,650us-gaap_DerivativeAssetNotionalAmount
Derivative Liabilities, Notional 1,499,720us-gaap_DerivativeLiabilityNotionalAmount 1,425,901us-gaap_DerivativeLiabilityNotionalAmount
Derivative Assets, Fair Value 9,557us-gaap_DerivativeFairValueOfDerivativeAsset 15,009us-gaap_DerivativeFairValueOfDerivativeAsset
Derivative Liabilities, Fair Value 48,604us-gaap_DerivativeFairValueOfDerivativeLiability 30,528us-gaap_DerivativeFairValueOfDerivativeLiability
Net Investment Hedges | Foreign Currency Contracts    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional   62,078us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_NetInvestmentHedgingMember
Derivative Liabilities, Notional 53,280us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_NetInvestmentHedgingMember
 
Derivative Assets, Fair Value   523us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_NetInvestmentHedgingMember
Derivative Liabilities, Fair Value 408us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_NetInvestmentHedgingMember
 
Freestanding Derivatives    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 443,088us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
657,572us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
Derivative Liabilities, Notional 1,446,440us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
1,425,901us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
Derivative Assets, Fair Value 9,557us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
14,486us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
Derivative Liabilities, Fair Value 48,196us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
30,528us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
Freestanding Derivatives | Foreign Currency Contracts | Blackstone - Other    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 158,470us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
192,163us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Notional 224,625us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
148,873us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Assets, Fair Value 1,647us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
2,798us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Fair Value 2,593us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
681us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Freestanding Derivatives | Foreign Currency Contracts | Investments Of Consolidated Blackstone Funds    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 135,520us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
199,364us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Derivative Liabilities, Notional 302,609us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
250,244us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Derivative Assets, Fair Value 5,118us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
8,915us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Derivative Liabilities, Fair Value 36,138us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
21,875us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForeignExchangeContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Freestanding Derivatives | Interest Rate Contracts | Blackstone - Other    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 109,405us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
223,886us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Notional 780,146us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
879,412us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Assets, Fair Value 451us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
407us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Fair Value 7,458us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
4,590us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Freestanding Derivatives | Interest Rate Contracts | Investments Of Consolidated Blackstone Funds    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 20,193us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
22,659us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Derivative Assets, Fair Value 2,033us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
2,281us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateContractMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Freestanding Derivatives | Credit Default Swaps | Blackstone - Other    
Derivatives, Fair Value [Line Items]    
Derivative Assets, Notional 19,500us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
19,500us-gaap_DerivativeAssetNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Notional 56,000us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
56,000us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Assets, Fair Value 308us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
85us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Derivative Liabilities, Fair Value 1,464us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
868us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_BlackstoneOtherMember
Freestanding Derivatives | Credit Default Swaps | Investments Of Consolidated Blackstone Funds    
Derivatives, Fair Value [Line Items]    
Derivative Liabilities, Notional 83,060us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
91,372us-gaap_DerivativeLiabilityNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
Derivative Liabilities, Fair Value $ 543us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember
$ 2,514us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= bx_CreditDefaultSwapsMember
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= bx_FreestandingDerivativesMember
/ dei_LegalEntityAxis
= bx_InvestmentsOfConsolidatedBlackstoneFundsMember