INVESTMENTS - Net Gains (Losses) from Investment Activities of Consolidated Funds (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	$ (17,773)	$ (23,528)	$ 20,400
Net Change in Unrealized Appreciation (Depreciation) on Investments	9,937	(164,592)	55,061
Consolidated Funds \| Not Designated as Hedging Instrument
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(17,773)	(23,528)	20,400
Net Change in Unrealized Appreciation (Depreciation) on Investments	9,937	(164,592)	55,061
Consolidated Funds \| Not Designated as Hedging Instrument \| Investments and other financial instruments
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(11,227)	(26,109)	27,910
Net Change in Unrealized Appreciation (Depreciation) on Investments	137,521	(252,038)	(1,151)
Consolidated Funds \| Not Designated as Hedging Instrument \| CLO liabilities
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	0	0	0
Net Change in Unrealized Appreciation (Depreciation) on Investments	(131,948)	85,014	53,351
Consolidated Funds \| Not Designated as Hedging Instrument \| Foreign-currency forward contracts
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(6,546)	513	(2,917)
Net Change in Unrealized Appreciation (Depreciation) on Investments	4,364	2,327	1,909
Consolidated Funds \| Not Designated as Hedging Instrument \| Total-return and interest-rate swaps
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	0	858	232
Net Change in Unrealized Appreciation (Depreciation) on Investments	0	29	378
Consolidated Funds \| Not Designated as Hedging Instrument \| Options and futures
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	0	1,210	(4,825)
Net Change in Unrealized Appreciation (Depreciation) on Investments	$ 0	$ 76	$ 574

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

+ Details

Name:	us-gaap_RealizedInvestmentGainsLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_UnrealizedGainLossOnInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=oak_InvestmentsAndOtherFinancialInstrumentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=oak_MeasurementAlternativeGuidanceForCLOsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=oak_ForeignCurrencyForwardContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=oak_TotalreturnAndInterestRateSwapsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=oak_OptionsAndFuturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: