SEGMENT REPORTING (Reconciliation of Income Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Economic net income
Income before taxes	$ 88,424	$ 125,425	$ 12,916	$ 199,457
Adjustments:
Equity compensation expenses	18,091	8,476	52,097	27,185
Income tax expense (benefit)	(4,552)	(7,641)	28,459	(7,868)
Operating segment
Economic net income
Income before taxes	88,424	125,425	12,916	199,457
Adjustments:
Amortization of intangibles	3,651	6,378	14,200	20,762
Depreciation expense	3,468	2,148	9,458	5,940
Equity compensation expenses	18,091	8,476	52,097	27,185
Acquisition and merger-related expenses	2,878	(17,611)	258,722	(17,054)
Placement fees and underwriting costs	4,495	2,202	14,317	4,886
Offering costs	33	0	688	0
Other non-cash expense	0	(1,728)	0	(1,728)
Economic net income	143,428	160,753	473,766	382,859
Total performance fees income - realized	(178,989)	(132,837)	(261,924)	(220,790)
Total performance fees income - unrealized	89,423	(32,368)	(223,467)	(118,334)
Total performance fee compensation - realized	(140,979)	(93,778)	(199,253)	(146,792)
Total performance fee compensation - unrealized	(82,342)	29,395	161,791	106,947
Total investment income	(8,563)	(34,040)	(49,720)	(51,685)
Fee related earnings	103,936	84,681	299,699	245,789
Investment and other income realized, net	21,160	14,777	27,067	33,605
Dividend equivalent	(3,540)	(1,649)	(7,741)	(3,039)
One-time acquisition costs	(12)	(12)	(35)	(294)
Income tax expense (benefit)	(343)	(292)	(950)	(773)
Non-cash items	397	36	533	883
Placement fees and underwriting costs	(4,495)	(2,209)	(14,317)	(4,894)
Depreciation and amortization	(1,448)	(960)	(4,233)	(2,889)
Distributable earnings	153,665	133,431	362,694	342,386
Economic net income	143,428	160,753	473,766	382,859
Performance related earnings	39,492	76,072	174,067	137,070
Operating segment | Subsidiaries
Adjustments:
(Income) loss before taxes of non-controlling interests in Consolidated Funds, net of eliminations	(216)	0	407	0
Reconciling items
Adjustments:
Amortization of intangibles	3,651	6,378	14,200	20,762
Depreciation expense	3,468	2,148	9,458	5,940
Equity compensation expenses	18,091	8,476	52,097	27,185
Acquisition and merger-related expenses	2,818	79	278,878	432
Placement fees and underwriting costs	4,495	2,202	14,317	4,886
Offering costs	33	0	688	0
Other non-cash expense	0	(1,728)	0	(1,728)
Total consolidation adjustments and reconciling items	55,004	35,328	460,850	183,402
OMG
Adjustments:
OMG expenses, net	41,997	44,021	138,426	139,628
Economic net income	(41,997)	(44,021)	(138,426)	(139,628)
Total performance fees income - realized	0	0	0	0
Total performance fees income - unrealized	0	0	0	0
Total performance fee compensation - realized	0	0	0	0
Total performance fee compensation - unrealized	0	0	0	0
Total investment income	(3,960)	4,675	(3,184)	17,787
Fee related earnings	(45,957)	(39,346)	(141,610)	(121,841)
Distributable earnings	(53,214)	(66,696)	(151,642)	(157,550)
Economic net income	(41,997)	(44,021)	(138,426)	(139,628)
Performance related earnings	3,960	(4,675)	3,184	(17,787)
Consolidated Funds
Adjustments:
(Income) loss before taxes of non-controlling interests in Consolidated Funds, net of eliminations	18,195	7,861	25,403	(3,064)
Total investment income	(20,054)	(8,737)	(41,675)	(25,759)
Consolidated Funds | Operating segment
Adjustments:
(Income) loss before taxes of non-controlling interests in Consolidated Funds, net of eliminations	$ (19,393)	$ (8,558)	$ (27,465)	$ 3,783