v2.4.1.9

Carrying Value and Fair Value of Blackstone Issued Notes (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2012
Debt Instrument [Line Items]
Senior Notes		$ 600us-gaap_SeniorNotes
Notes acquired not retired		15bx_NotesAcquiredNotRetired
6.625% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	6.625%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_SixPointSixTwoFivePercentNotesMember
Debt instrument, maturity date	Aug. 15, 2019
Senior Notes	600us-gaap_SeniorNotes / us-gaap_DebtInstrumentAxis = bx_SixPointSixTwoFivePercentNotesMember
5.875% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	5.875%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_FivePointEightSevenFivePercentNotesMember
Debt instrument, maturity date	Mar. 15, 2021
Senior Notes	400us-gaap_SeniorNotes / us-gaap_DebtInstrumentAxis = bx_FivePointEightSevenFivePercentNotesMember
4.750% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_FourPointSevenFiveZeroPercentNotesMember
Debt instrument, maturity date	Feb. 15, 2023
Senior Notes	400us-gaap_SeniorNotes / us-gaap_DebtInstrumentAxis = bx_FourPointSevenFiveZeroPercentNotesMember
6.250% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	6.25%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_SixPointTwoFiveZeroPercentNotesMember
Debt instrument, maturity date	Aug. 15, 2042
Senior Notes	250us-gaap_SeniorNotes / us-gaap_DebtInstrumentAxis = bx_SixPointTwoFiveZeroPercentNotesMember
5.000% Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = bx_FivePointZeroZeroZeroPercentNotesMember
Debt instrument, maturity date	Jun. 15, 2044
Senior Notes	$ 500us-gaap_SeniorNotes / us-gaap_DebtInstrumentAxis = bx_FivePointZeroZeroZeroPercentNotesMember

X

- Definition

Notes Acquired but not Retired.

+ References

No definition available.

+ Details

Name:	bx_NotesAcquiredNotRetired
Namespace Prefix:	bx_
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

- Details

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

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bx_FivePointEightSevenFivePercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bx_FivePointZeroZeroZeroPercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bx_FourPointSevenFiveZeroPercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bx_SixPointSixTwoFivePercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bx_SixPointTwoFiveZeroPercentNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: