v3.3.0.814

Offsetting Of Assets And Liabilities - Additional Information (Detail) $ in Billions	Sep. 30, 2015 USD ($)
Cash Pooling Arrangement
Offsetting Assets [Line Items]
Aggregate cash balance on deposit relating to the cash pooling arrangement	$ 1.2

X

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Glossary Cash



-URI http://asc.fasb.org/extlink&oid=6506951



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 210.5-02.1)



-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_Cash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_TransactionTypeAxis=bx_CashPoolingArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: