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 | $ 1,600,000,000 bx_GeneralPartnerCapitalFundingCommitments
Total investments at risk in respect of guarantees extended | 8,300,000 us-gaap_FairValueConcentrationOfRiskInvestments
Contingent obligations currently anticipated to expire end | 2016
Provision for cash clawback | 496,100,000 bx_ProvisionForCashClawback
Blackstone Holdings Finance Co. L.L.C. |
Schedule Of Commitments And Contingencies [Line Items] |
Loans held By employees for investment guaranteed | 89,700,000 bx_LoansHeldByEmployeesForInvestmentGuaranteed / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember
Blackstone Group L P |
Schedule Of Commitments And Contingencies [Line Items] |
Loans held By employees for investment guaranteed | 18,800,000 bx_LoansHeldByEmployeesForInvestmentGuaranteed / dei_LegalEntityAxis = bx_BlackstoneGroupLPMember
Blackstone Funds |
Schedule Of Commitments And Contingencies [Line Items] |
Funds signed investment commitments | 27,800,000 bx_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 | $ 11,600,000 bx_SignedInvestmentCommitmentsForPortfolioCompanyAcquisitionsInProcessOfClosing / us-gaap_InvestmentTypeAxis = bx_PortfolioCompanyAcquisitionMember / us-gaap_StatementBusinessSegmentsAxis = bx_BlackstoneFundsMember

X
- Definition Contingent obligations currently anticipated to expire end + References No definition available. + Details
Name: | bx_ContingentObligationsCurrentlyAnticipatedToExpireEnd
Namespace Prefix: | bx_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Funds Signed Investment Commitments + References No definition available. + Details
Name: | bx_FundsSignedInvestmentCommitments
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition General Partner Capital Funding Commitments + References No definition available. + Details
Name: | bx_GeneralPartnerCapitalFundingCommitments
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loans Held By Employees For Investment Guaranteed + References No definition available. + Details
Name: | bx_LoansHeldByEmployeesForInvestmentGuaranteed
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Provision for cash clawback + References No definition available. + Details
Name: | bx_ProvisionForCashClawback
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | bx_ScheduleOfCommitmentsAndContingenciesLineItems
Namespace Prefix: | bx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Signed Investment Commitments For Portfolio Company Acquisitions In Process Of Closing + References No definition available. + Details
Name: | bx_SignedInvestmentCommitmentsForPortfolioCompanyAcquisitionsInProcessOfClosing
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 + Details
Name: | us-gaap_FairValueConcentrationOfRiskInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=bx_BlackstoneGroupLPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=bx_BlackstoneHoldingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=bx_BlackstoneFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |