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
	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	$ 350us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = bx_FourPointFourFiveZeroPercentageSeniorNotesMember / dei_LegalEntityAxis = bx_BlackstoneHoldingsMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember	$ 350us-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

X

- 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

X

- 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

X

- 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

X

- Details

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