REVENUES - Revenues Disaggregated by Fund Structure (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 43,919	$ 266,415
Management Fees
Disaggregation of Revenue [Line Items]
Revenues	41,524	169,934
Closed-end
Disaggregation of Revenue [Line Items]
Revenues	316	109,375
Open-end
Disaggregation of Revenue [Line Items]
Revenues	1,820	31,541
Evergreen
Disaggregation of Revenue [Line Items]
Revenues	0	29,018
Sub-advisory fees
Disaggregation of Revenue [Line Items]
Revenues	39,388	0
Incentive Income
Disaggregation of Revenue [Line Items]
Revenues	$ 2,400	$ 96,500

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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