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
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Mar. 31, 2015 | Mar. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Balance, Beginning of Period | $ 6,797,104 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue | $ 8,913,007 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
Transfer In Due to Consolidation and Acquisition |  | 558,201 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet | [1]
Transfer Out to Deconsolidation |  | (678,889)bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesTransferInOutDueToDeconsolidation |
Issuances | 931,159 us-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 | 2,538 bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss |
Balance, End of Period | 6,933,747 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue | 8,405,760 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue |
Changes in Unrealized (Gains) Losses Included in Earnings Related to Liabilities Still Held at the Reporting Date | (6,471)us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss | 8,951 us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss |
Collateralized Loan Obligations Senior Notes |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Balance, Beginning of Period | 6,448,352 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember | 8,302,572 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember |
Transfer In Due to Consolidation and Acquisition |  | 472,019 us-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 | 888,960 us-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 | 2,538 bx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInEarningsAndOtherComprehensiveIncomeLoss / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember |
Balance, End of Period | 6,587,954 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSeniorNotesMember | 7,749,051 us-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 | 46,472 us-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 | 348,752 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember | 610,435 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember |
Transfer In Due to Consolidation and Acquisition |  | 86,182 us-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 | 42,199 us-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 | 345,793 us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_InvestmentTypeAxis = bx_CollateralizedLoanObligationsSubordinatedNotesMember | 656,709 us-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 | $ 19,698 us-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.

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- Definition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liabilities, Gain (Loss) Included in Earnings And Other Comprehensive Income (Loss) + References No definition available. + Details
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- Definition Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liabilities Transfer In (Out) Due To Deconsolidation + References No definition available. + Details
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- Definition Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy. + References No definition available. + Details
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- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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