v2.4.1.9

Borrowings - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Fair value of the CLO assets	$ 8.2bx_FairValueOfCLOAssets	$ 8.0bx_FairValueOfCLOAssets

X

- Definition

Fair Value of the CLO Assets

+ References

No definition available.

+ Details

Name:	bx_FairValueOfCLOAssets
Namespace Prefix:	bx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

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