v2.4.1.9
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
Mar. 31, 2015
Mar. 31, 2014
Blackstone's Treasury Cash Management Strategies
    
Gain (Loss) on Investments [Line Items]    
Realized Gains (Losses) $ (161)bx_RealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember		 $ 3,094bx_RealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember
Net Change in Unrealized Gains 11,111bx_NetChangesInUnrealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember		 8,970bx_NetChangesInUnrealizedGainsLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember
Total realized and net change in unrealized gains (losses) $ 10,950bx_RealizedGainsLossesAndNetChangeInUnrealizedGainsAndLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember		 $ 12,064bx_RealizedGainsLossesAndNetChangeInUnrealizedGainsAndLossesOnInvestmentsHeldByTreasuryCashManagementStrategies
/ dei_LegalEntityAxis
= bx_BlackstoneTreasuryCashManagementStrategiesMember