INVESTMENTS - Net Gains (Losses) from Investment Activities of Consolidated Funds (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	$ 235	$ 6,682	$ (1,637)	$ 10,083
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	28,453	(5,301)	53,131	(25,973)
Consolidated Funds \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	235	6,682	(1,637)	10,083
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	28,453	(5,301)	53,131	(25,973)
Consolidated Funds \| Investments and other financial instruments \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	1,497	8,651	2,236	12,322
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	5,193	17,740	8,929	27,423
Consolidated Funds \| CLO Liabilities \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	0	0	0	0
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	23,517	(24,172)	43,348	(52,374)
Consolidated Funds \| Foreign-currency forward contracts \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	(569)	(298)	(390)	(500)
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	(96)	849	(410)	457
Consolidated Funds \| Total-return and interest-rate swaps \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	(722)	(907)	(1,468)	(890)
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	(237)	222	998	(1,396)
Consolidated Funds \| Options and futures \| Not Designated as Hedging Instrument
Gain (Loss) on Investments [Line Items]
Net realized gain (loss) on consolidated funds’ investments	29	(764)	(2,015)	(849)
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	$ 76	$ 60	$ 266	$ (83)

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 325
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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