v2.4.1.9
Commitments and Contingencies - Additional Information (Detail) (USD $)
 3 Months Ended
Mar. 31, 2015
Schedule Of Commitments And Contingencies [Line Items]  
General partner capital funding $ 1,600,000,000bx_GeneralPartnerCapitalFundingCommitments
Total investments at risk in respect of guarantees extended 8,300,000us-gaap_FairValueConcentrationOfRiskInvestments
Contingent obligations currently anticipated to expire end 2016
Provision for cash clawback 496,100,000bx_ProvisionForCashClawback
Blackstone Holdings Finance Co. L.L.C.  
Schedule Of Commitments And Contingencies [Line Items]  
Loans held By employees for investment guaranteed 89,700,000bx_LoansHeldByEmployeesForInvestmentGuaranteed
/ dei_LegalEntityAxis
= bx_BlackstoneHoldingsMember
Blackstone Group L P  
Schedule Of Commitments And Contingencies [Line Items]  
Loans held By employees for investment guaranteed 18,800,000bx_LoansHeldByEmployeesForInvestmentGuaranteed
/ dei_LegalEntityAxis
= bx_BlackstoneGroupLPMember
Blackstone Funds  
Schedule Of Commitments And Contingencies [Line Items]  
Funds signed investment commitments 27,800,000bx_FundsSignedInvestmentCommitments
/ us-gaap_StatementBusinessSegmentsAxis
= bx_BlackstoneFundsMember
Blackstone Funds | Portfolio Company Acquisition  
Schedule Of Commitments And Contingencies [Line Items]  
Signed investment commitments for portfolio company acquisitions in process of closing $ 11,600,000bx_SignedInvestmentCommitmentsForPortfolioCompanyAcquisitionsInProcessOfClosing
/ us-gaap_InvestmentTypeAxis
= bx_PortfolioCompanyAcquisitionMember
/ us-gaap_StatementBusinessSegmentsAxis
= bx_BlackstoneFundsMember