v2.4.1.9
Summary of Changes in Financial Liabilities Measured at Fair Value for Which Level III Inputs Were Used (Detail) (Level 3, USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Balance, Beginning of Period $ 6,797,104us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue $ 8,913,007us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Transfer In Due to Consolidation and Acquisition   558,201us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet [1]
Transfer Out to Deconsolidation   (678,889)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation
Issuances 931,159us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues  
Settlements (266,317)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements (389,097)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
Changes in (Gains) Losses Included in Earnings and Other Comprehensive Income (528,199)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss 2,538bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss
Balance, End of Period 6,933,747us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue 8,405,760us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Changes in Unrealized (Gains) Losses Included in Earnings Related to Liabilities Still Held at the Reporting Date (6,471)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss 8,951us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Collateralized Loan Obligations Senior Notes
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Balance, Beginning of Period 6,448,352us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
8,302,572us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Transfer In Due to Consolidation and Acquisition   472,019us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
[1]
Transfer Out to Deconsolidation   (639,091)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Issuances 888,960us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
 
Settlements (266,317)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
(388,987)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Changes in (Gains) Losses Included in Earnings and Other Comprehensive Income (483,041)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
2,538bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Balance, End of Period 6,587,954us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
7,749,051us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Changes in Unrealized (Gains) Losses Included in Earnings Related to Liabilities Still Held at the Reporting Date (26,169)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
46,472us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSeniorNotesMember
Collateralized Loan Obligations Subordinated Notes
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Balance, Beginning of Period 348,752us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
610,435us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
Transfer In Due to Consolidation and Acquisition   86,182us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
[1]
Transfer Out to Deconsolidation   (39,798)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
Issuances 42,199us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
 
Settlements   (110)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
Changes in (Gains) Losses Included in Earnings and Other Comprehensive Income (45,158)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
 
Balance, End of Period 345,793us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
656,709us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
Changes in Unrealized (Gains) Losses Included in Earnings Related to Liabilities Still Held at the Reporting Date $ 19,698us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
$ (37,521)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= bx_CollateralizedLoanObligationsSubordinatedNotesMember
[1] Represents the transfer into Level III of financial assets and liabilities as a result of the consolidation of certain fund entities, the acquisition of management contracts and the Harbourmaster acquisition.