v2.4.1.9

Assets and Liabilities Related to Interest in Non-Consolidated VIEs and Maximum Exposure to Loss (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
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Variable Interest Entity [Line Items] |  |
Investments | $ 813,764 bx_VieCarryingAmountOfInvestmentsUnconsolidatedVie | $ 776,079 bx_VieCarryingAmountOfInvestmentsUnconsolidatedVie
Accounts Receivable | 103,400 bx_VieCarryingAmountOfReceivablesUnconsolidatedVie | 125,316 bx_VieCarryingAmountOfReceivablesUnconsolidatedVie
Due from Affiliates | 45,788 bx_VariableInterestEntityConsolidatedCarryingAmountDueFromAffiliates | 53,751 bx_VariableInterestEntityConsolidatedCarryingAmountDueFromAffiliates
Total VIE Assets | 962,952 us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets | 955,146 us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Due to Affiliates | 94 bx_VariableInterestEntityConsolidatedCarryingAmountDueToAffiliates | 108 bx_VariableInterestEntityConsolidatedCarryingAmountDueToAffiliates
Accounts Payable, Accrued Expenses and Other Liabilities | 44 bx_VariableInterestEntityConsolidatedCarryingAmountAccountsPayableAccruedExpensesAndOtherLiabilities | 124 bx_VariableInterestEntityConsolidatedCarryingAmountAccountsPayableAccruedExpensesAndOtherLiabilities
Potential Clawback Obligation | 245,651 bx_PotentialClawbackObligationOfNonConsolidatedVie | 206,725 bx_PotentialClawbackObligationOfNonConsolidatedVie
Maximum Exposure to Loss | $ 1,208,741 us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount | $ 1,162,103 us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount

X
- Definition Potential Clawback Obligation of Non-consolidated VIE + References No definition available. + Details
Name: | bx_PotentialClawbackObligationOfNonConsolidatedVie
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Variable Interest Entity Consolidated Carrying Amount Accounts Payable, Accrued Expenses and Other Liabilities + References No definition available. + Details
Name: | bx_VariableInterestEntityConsolidatedCarryingAmountAccountsPayableAccruedExpensesAndOtherLiabilities
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Variable Interest Entity Consolidated Carrying Amount Due from Affiliates + References No definition available. + Details
Name: | bx_VariableInterestEntityConsolidatedCarryingAmountDueFromAffiliates
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Variable Interest Entity Consolidated Carrying Amount Due to Affiliates + References No definition available. + Details
Name: | bx_VariableInterestEntityConsolidatedCarryingAmountDueToAffiliates
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition VIE Carrying Amount of Investments Unconsolidated VIE + References No definition available. + Details
Name: | bx_VieCarryingAmountOfInvestmentsUnconsolidatedVie
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition VIE Carrying Amount of Receivables Unconsolidated VIE + References No definition available. + Details
Name: | bx_VieCarryingAmountOfReceivablesUnconsolidatedVie
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5747-111685 + Details
Name: | us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph a -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685 + Details
Name: | us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant