v2.4.1.9
Summary of Financial Instruments for Which Fair Value Option Has Been Elected (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity and Preferred Securities $ 103,971bx_EquityAndPreferredSecurities $ 102,907bx_EquityAndPreferredSecurities
Total Assets 6,444,914us-gaap_AssetsFairValueDisclosure 6,760,099us-gaap_AssetsFairValueDisclosure
Total Liabilities 6,933,747us-gaap_LiabilitiesFairValueDisclosure 6,797,104us-gaap_LiabilitiesFairValueDisclosure
Corporate Bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets of Consolidated CLO Vehicles: Corporate Bonds 322,696bx_AssetsOfConsolidatedCloVehiclesCorporateBondsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateBondSecuritiesMember		 292,690bx_AssetsOfConsolidatedCloVehiclesCorporateBondsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateBondSecuritiesMember
Senior Secured Notes | Liabilities of Consolidated CLO Vehicles    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of Notes 6,587,954us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByLiabilityClassAxis
= bx_LiabilitiesOfConsolidatedCloVehiclesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_SeniorNotesMember		 [1] 6,448,352us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByLiabilityClassAxis
= bx_LiabilitiesOfConsolidatedCloVehiclesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_SeniorNotesMember		 [1]
Subordinated Notes | Liabilities of Consolidated CLO Vehicles    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair value of Notes 345,793us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByLiabilityClassAxis
= bx_LiabilitiesOfConsolidatedCloVehiclesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_SeniorSubordinatedNotesMember		 [1] 348,752us-gaap_NotesPayableFairValueDisclosure
/ us-gaap_FairValueByLiabilityClassAxis
= bx_LiabilitiesOfConsolidatedCloVehiclesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_SeniorSubordinatedNotesMember		 [1]
Other    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets of Consolidated CLO Vehicles: Other 75,387bx_AssetsOfConsolidatedCloVehiclesOtherFairValueDisclosure
/ us-gaap_UnderlyingAssetClassAxis
= us-gaap_CollateralizedSecuritiesOtherMember		 44,513bx_AssetsOfConsolidatedCloVehiclesOtherFairValueDisclosure
/ us-gaap_UnderlyingAssetClassAxis
= us-gaap_CollateralizedSecuritiesOtherMember
Loans And Receivables    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Loans and Receivables 40,691us-gaap_LoansReceivableFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= bx_LoansAndReceivablesMember		 40,397us-gaap_LoansReceivableFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= bx_LoansAndReceivablesMember
Corporate Loans    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets of Consolidated CLO Vehicles: Corporate Loans $ 5,902,169bx_AssetsOfConsolidatedCloVehiclesCorporateLoansFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 $ 6,279,592bx_AssetsOfConsolidatedCloVehiclesCorporateLoansFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
[1] Pursuant to GAAP consolidation guidance, the Partnership is required to consolidate all VIEs in which it has been identified as the primary beneficiary, including certain CLO vehicles, and other funds in which a consolidated entity of the Partnership, as the general partner of the fund, is presumed to have control. While the Partnership is required to consolidate certain funds, including CLO vehicles, for GAAP purposes, the Partnership has no ability to utilize the assets of these funds and there is no recourse to the Partnership for their liabilities since these are client assets and liabilities.