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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
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3 Months Ended |
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Mar. 31, 2015
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Mar. 31, 2014
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| Balance, Beginning of Period |
$ 6,797,104us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
$ 8,913,007us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
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| Transfer In Due to Consolidation and Acquisition |
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558,201us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet |
[1] |
| Transfer Out to Deconsolidation |
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(678,889)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation |
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| Issuances |
931,159us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues |
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| Settlements |
(266,317)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements |
(389,097)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements |
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| Changes in (Gains) Losses Included in Earnings and Other Comprehensive Income |
(528,199)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss |
2,538bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss |
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| Balance, End of Period |
6,933,747us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
8,405,760us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
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| 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 |
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Collateralized Loan Obligations Senior Notes
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| 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 |
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| Transfer In Due to Consolidation and Acquisition |
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472,019us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember |
[1] |
| Transfer Out to Deconsolidation |
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(639,091)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember |
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| Issuances |
888,960us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember |
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| 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 |
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| 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 |
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| 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 |
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| 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 |
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Collateralized Loan Obligations Subordinated Notes
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
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| 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 |
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| Transfer In Due to Consolidation and Acquisition |
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86,182us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember |
[1] |
| Transfer Out to Deconsolidation |
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(39,798)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember |
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| Issuances |
42,199us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember |
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| Settlements |
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(110)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember |
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| 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 |
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| 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 |
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| 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 |
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