DEBT OBLIGATIONS AND CREDIT FACILITIES - Collateralized Loan Obligation Loans Payable (Details) - Consolidated Funds - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt obligations	$ 2,840,252	$ 2,330,359
Assets backing the obligation	3,300,000	2,600,000
Collateralized Loan Obligations
Debt Instrument [Line Items]
Carrying Value	2,840,252	2,355,060
Less: Debt issuance costs	0	(24,701)
Debt obligations	2,840,252	2,330,359
Collateralized Loan Obligations \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		2,294,938
Collateralized Loan Obligations \| Senior variable rate notes 1
Debt Instrument [Line Items]
Carrying Value	$ 465,387	$ 457,196
Weighted average interest rate (as a percent)	2.82%	2.37%
Weighted Average Remaining Maturity (in years)	8 years 6 months	9 years 3 months 18 days
Collateralized Loan Obligations \| Senior variable rate notes 1 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 447,460
Collateralized Loan Obligations \| Senior variable rate notes 2
Debt Instrument [Line Items]
Carrying Value	$ 464,430	$ 454,423
Weighted average interest rate (as a percent)	2.86%	2.52%
Weighted Average Remaining Maturity (in years)	10 years 2 months 12 days	11 years
Collateralized Loan Obligations \| Senior variable rate notes 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 446,558
Collateralized Loan Obligations \| Senior variable rate notes 3
Debt Instrument [Line Items]
Carrying Value	$ 54,868	$ 79,914
Weighted average interest rate (as a percent)	3.16%	2.96%
Weighted Average Remaining Maturity (in years)	2 years 3 months 18 days	3 years
Collateralized Loan Obligations \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 78,632
Collateralized Loan Obligations \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement \| Minimum
Debt Instrument [Line Items]
Unused commitment fee (as a percent)	0.00%
Collateralized Loan Obligations \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement \| Maximum
Debt Instrument [Line Items]
Unused commitment fee (as a percent)	2.00%
Collateralized Loan Obligations \| Senior variable rate notes 4
Debt Instrument [Line Items]
Carrying Value	$ 381,266	$ 363,709
Weighted average interest rate (as a percent)	2.26%	2.26%
Weighted Average Remaining Maturity (in years)	10 years 10 months 24 days	11 years 8 months 12 days
Collateralized Loan Obligations \| Senior variable rate notes 4 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 357,626
Collateralized Loan Obligations \| Senior variable rate notes 4 \| Estimate of Fair Value Measurement \| EURIBOR
Debt Instrument [Line Items]
Base rate (as a percent)	0.00%
Collateralized Loan Obligations \| Senior variable rate notes 5
Debt Instrument [Line Items]
Carrying Value	$ 463,936	$ 455,295
Weighted average interest rate (as a percent)	2.78%	2.54%
Weighted Average Remaining Maturity (in years)	11 years 2 months 12 days	12 years
Collateralized Loan Obligations \| Senior variable rate notes 5 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 448,933
Collateralized Loan Obligations \| Senior variable rate notes 6
Debt Instrument [Line Items]
Carrying Value	$ 382,650	$ 361,142
Weighted average interest rate (as a percent)	2.29%	2.29%
Weighted Average Remaining Maturity (in years)	11 years 6 months	12 years 3 months 18 days
Collateralized Loan Obligations \| Senior variable rate notes 6 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 359,914
Collateralized Loan Obligations \| Senior variable rate notes 7
Debt Instrument [Line Items]
Carrying Value	$ 415,552
Weighted average interest rate (as a percent)	2.28%
Weighted Average Remaining Maturity (in years)	12 years 7 months 6 days
Collateralized Loan Obligations \| Subordinated note 1
Debt Instrument [Line Items]
Carrying Value	$ 11,823	$ 25,500
Weighted Average Remaining Maturity (in years)	10 years 2 months 12 days	11 years
Collateralized Loan Obligations \| Subordinated note 1 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 16,400
Collateralized Loan Obligations \| Subordinated note 2
Debt Instrument [Line Items]
Carrying Value	$ 17,975	$ 21,183
Weighted Average Remaining Maturity (in years)	10 years 10 months 24 days	11 years 8 months 21 days
Collateralized Loan Obligations \| Subordinated note 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 15,876
Collateralized Loan Obligations \| Subordinated note 3
Debt Instrument [Line Items]
Carrying Value	$ 18,827	$ 25,500
Weighted Average Remaining Maturity (in years)	11 years 2 months 12 days	12 years
Collateralized Loan Obligations \| Subordinated note 3 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 18,337
Collateralized Loan Obligations \| Subordinated note 4
Debt Instrument [Line Items]
Carrying Value	$ 14,764	$ 17,924
Weighted Average Remaining Maturity (in years)	11 years 6 months	12 years 3 months 18 days
Collateralized Loan Obligations \| Subordinated note 4 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 11,928
Collateralized Loan Obligations \| Subordinated note 5
Debt Instrument [Line Items]
Carrying Value	$ 20,441	$ 12,036
Weighted Average Remaining Maturity (in years)	12 years 7 months 6 days	1 year 7 months 6 days
Collateralized Loan Obligations \| Subordinated note 5 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 12,036
Collateralized Loan Obligations \| Subordinated note 6
Debt Instrument [Line Items]
Carrying Value	$ 21,086
Weighted Average Remaining Maturity (in years)	1 year 9 months 18 days
Collateralized Loan Obligations \| Term loan 1
Debt Instrument [Line Items]
Carrying Value	$ 107,247
Weighted average interest rate (as a percent)	1.20%
Weighted Average Remaining Maturity (in years)	1 year 9 months 18 days
Collateralized Loan Obligations \| Term loan 2
Debt Instrument [Line Items]
Carrying Value		$ 81,238
Weighted average interest rate (as a percent)		1.20%
Weighted Average Remaining Maturity (in years)		1 year 7 months 6 days
Collateralized Loan Obligations \| Term loan 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 81,238

Debt Instrument, Base Rate Floor

No definition available.

Name:	oak_DebtInstrumentBaseRateFloor
Namespace Prefix:	oak_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Weighted Average Remaining Term

+ References

No definition available.

+ Details

Name:	oak_DebtInstrumentWeightedAverageRemainingTerm
Namespace Prefix:	oak_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_SecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

+ Details

Name:	us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant