v2.4.0.8

Realized and Net Change in Unrealized Gains (Losses) on Investments Held by Blackstone's Treasury Cash Management Strategies (Detail) (Blackstone's Treasury Cash Management Strategies, USD $) In Thousands, unless otherwise specified | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012
Blackstone's Treasury Cash Management Strategies |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |
Realized Gains (Losses) | $ (6,587) | $ 3,228 | $ (4,030) | $ 3,238
Net Change in Unrealized Gains (Losses) | 10,126 | 6,525 | (9,041) | 7,351
Total realized and net change in unrealized gains (losses) | $ 3,539 | $ 9,753 | $ (13,071) | $ 10,589

X
- Definition Net Changes In Unrealized Gains Losses On Investments Held By Treasury Cash Management Strategies + References No definition available. + Details
Name: | bx_NetChangesInUnrealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Realized Gains Losses On Investments Held By Treasury Cash Management Strategies + References No definition available. + Details
Name: | bx_RealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Total Realized Gains Losses and Net Change In Unrealized Gains Losses On Investments Held By Treasury Cash Management Strategies + References No definition available. + Details
Name: | bx_TotalRealizedGainsLossesAndNetChangeInUnrealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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