v2.4.1.9

Subsequent Event - Additional Information (Detail) (Subsequent Event, Blackstone Holdings Finance Co. L.L.C., Four Point Four Five Zero Percentage Senior Notes, USD $) In Millions, unless otherwise specified | 0 Months Ended |
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Apr. 27, 2015 | Apr. 27, 2015
Subsequent Event | Blackstone Holdings Finance Co. L.L.C. | Four Point Four Five Zero Percentage Senior Notes |  |
Subsequent Event [Line Items] |  |
Debt instrument, principal amount | $ 350 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bx_FourPointFourFiveZeroPercentageSeniorNotesMember / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember | $ 350 us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bx_FourPointFourFiveZeroPercentageSeniorNotesMember / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Debt instrument, interest rate | 4.45%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_FourPointFourFiveZeroPercentageSeniorNotesMember / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember | 4.45%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_FourPointFourFiveZeroPercentageSeniorNotesMember / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Debt instrument, maturity date | Jul. 15, 2045 |

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- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentMaturityDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

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