v2.4.1.9
Summary of Fair Value by Strategy Type Alongside Consolidated Funds of Hedge Funds' Remaining Unfunded Commitments and Ability to Redeem Such Investments (Parenthetical) (Detail)
Mar. 31, 2015
Diversified Instruments  
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]  
Percentage of investments unable to be redeemed at, or within 3 months of reporting date 81.00%us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareRedemptionRestrictionPercentage
/ us-gaap_InvestmentTypeAxis
= bx_DiversifiedInstrumentsMember
Percentage of investments in hedge funds in process of liquidation 13.00%us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerSharePlannedSaleInvestmentsNotIdentifiedPercentage
/ us-gaap_InvestmentTypeAxis
= bx_DiversifiedInstrumentsMember
Percentage of investments side pocketed as of reporting date 6.00%bx_PercentageOfInvestmentsSidePocketedAsOfReportingDate
/ us-gaap_InvestmentTypeAxis
= bx_DiversifiedInstrumentsMember
Percentage of investments redeemable as of reporting date 7.00%bx_PercentageOfInvestmentsRedeemableAsOfReportingDate
/ us-gaap_InvestmentTypeAxis
= bx_DiversifiedInstrumentsMember
Credit Driven  
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]  
Percentage of investments unable to be redeemed at, or within 3 months of reporting date 66.00%us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareRedemptionRestrictionPercentage
/ us-gaap_InvestmentTypeAxis
= bx_CreditDrivenMember
Percentage of investments in hedge funds in process of liquidation 1.00%us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerSharePlannedSaleInvestmentsNotIdentifiedPercentage
/ us-gaap_InvestmentTypeAxis
= bx_CreditDrivenMember
Percentage of investments redeemable as of reporting date 3.00%bx_PercentageOfInvestmentsRedeemableAsOfReportingDate
/ us-gaap_InvestmentTypeAxis
= bx_CreditDrivenMember
Percentage of investments elected to side pocket 30.00%bx_PercentageOfInvestmentsInCategoryRedemptionDiscretionOfInvesteeFundManagerElectingToSidePocketInvestments
/ us-gaap_InvestmentTypeAxis
= bx_CreditDrivenMember
Commodities  
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]  
Percentage of investments unable to be redeemed at, or within 3 months of reporting date 4.00%us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareRedemptionRestrictionPercentage
/ us-gaap_InvestmentTypeAxis
= bx_CommoditiesMember
Percentage of investment for which withdrawals are not permitted 96.00%bx_PercentageOfRestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= bx_CommoditiesMember