SEGMENT REPORTING (Reconciliation of Income Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								8 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Economic net income
Income (loss) before provision for income taxes	$ 136,943	$ 88,424	$ 115,080	$ (190,588)	$ 98,463	$ 125,425	$ 83,006	$ (8,974)		$ 149,859	$ 297,920	$ 81,484
Adjustments:
Depreciation expense										12,600	8,200	6,900
Equity compensation expense									$ 32,244	69,711	39,065
Performance Fees
Total investment (income) loss - realized										(29,917)	(50,414)	(25,638)
Fee related earnings
Income tax expense										23,052	(11,019)	(19,064)
Operating segment
Economic net income
Income (loss) before provision for income taxes										149,859	297,920	81,484
Adjustments:
Amortization of intangibles										17,850	26,638	46,227
Depreciation expense										12,631	8,215	6,942
Equity compensation expense										69,711	39,065	32,244
Acquisition and merger-related expenses										259,899	(16,902)	34,864
Placement fees and underwriting costs										19,765	6,424	8,825
Offering costs										688	0	0
Other non-cash expense										(1,730)	(1,728)	110
Economic net income										644,580	536,727	360,165
Total performance fees income - unrealized										(325,915)	(228,472)	(31,647)
Total performance fee compensation - unrealized										237,392	189,582	46,492
Total investment (income) loss - unrealized										(44,992)	(19,976)	27,414
Realized income										511,065	477,861	402,424
Performance Fees
Total performance fees income - realized										(317,787)	(292,998)	(121,948)
Total performance fee compensation - realized										242,330	198,264	65,191
Fee related earnings
Performance fees—realized										317,787	292,998	121,948
Performance fee compensation—realized										(242,330)	(198,264)	(65,191)
Investment and other income realized, net										29,913	50,415	25,638
Dividend equivalent										(12,427)	(4,181)	(2,688)
One-time acquisition costs										(118)	(457)	(1,553)
Income tax expense										(1,677)	(3,199)	(1,462)
Non-cash items										720	870	(758)
Placement fees and underwriting costs, noncorporate										(16,324)	(6,431)	(8,817)
Depreciation and amortization										(5,576)	(3,916)	(3,918)
Distributable earnings										475,659	460,548	383,228
Less: fee related earnings										405,691	332,713	320,029
Performance related earnings										238,889	204,014	40,136
OMG
Adjustments:
OMG expenses, net										176,873	179,744	143,787
Economic net income										(176,873)	(179,744)	(143,787)
Total investment (income) loss - unrealized										(8,627)	2,197	(52)
Realized income										(185,625)	(177,533)	(143,839)
Performance Fees
Total performance fees income - realized										0	0	0
Total performance fee compensation - realized										0	0	0
Total investment (income) loss - realized										11,828	(19,381)	(750)
Fee related earnings
Distributable earnings										(204,024)	(196,242)	(152,639)
Less: fee related earnings										(188,701)	(160,363)	(143,037)
Performance related earnings										11,828	(19,381)	(750)
Reconciling items
Adjustments:
Amortization of intangibles										17,850	26,638	46,227
Depreciation expense										12,631	8,215	6,942
Equity compensation expense										69,711	39,065	32,244
Acquisition and merger-related expenses										280,055	773	40,482
Placement fees and underwriting costs										19,765	6,424	8,825
Offering costs										688	0	0
Other non-cash expense										(1,730)	(1,728)	110
Total consolidation adjustments and reconciling items										494,721	238,807	278,681
Consolidated Funds
Adjustments:
Less: Net income attributable to non-controlling interests										60,818	3,386	(5,686)
Fee related earnings
Income tax expense										(1,887)	737	(4)
Consolidated Funds | Operating segment
Adjustments:
Less: Net income attributable to non-controlling interests										(62,705)	(2,649)	5,682
Subsidiaries | Operating segment
Adjustments:
Less: Net income attributable to non-controlling interests										$ 1,739	$ 0	$ 0