v2.4.0.6

Information for Financial Instruments on Which Fair Value Option was Elected (Parenthetical) (Detail) | Jun. 30, 2012 Day | Dec. 31, 2011 Day
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Loans and bonds contractual payment past due, number days | 1 | 1

X
- Definition Loans And Bonds Contractual Payment Past Due Number Days + References No definition available. + Details
Name: | bx_LoansAndBondsContractualPaymentPastDueNumberDays
Namespace Prefix: | bx_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | instant

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