SEGMENT REPORTING - Revenues Disaggregated By Business Line (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	$ 491,503	$ 355,418	$ 1,299,743	$ 1,116,382
Carried Interest	543,750	337,459	1,097,673	1,224,235
Total Investment Income (Loss)	833,288	177,953	2,748,604	1,289,638
Total Revenues	1,129,666	749,652	2,573,892	2,533,207
Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	503,614	355,716	1,283,548	1,096,398
Carried Interest	414,609	419,438	959,253	890,310
Incentive Fees	18,001	4,074	52,059	8,384
Total Realized Performance Income (Loss)	432,610	423,512	1,011,312	898,694
Net Realized Gains (Losses)	181,026	76,053	286,381	162,684
Interest Income and Dividends	61,717	70,557	205,522	195,275
Total Investment Income (Loss)	242,743	146,610	491,903	357,959
Total Revenues	1,178,967	925,838	2,786,763	2,353,051
Private Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	216,542	190,587	584,615	537,816
Carried Interest	404,709	419,438	949,353	890,310
Incentive Fees	0	0	0	0
Total Realized Performance Income (Loss)	404,709	419,438	949,353	890,310
Net Realized Gains (Losses)	0	0	0	0
Interest Income and Dividends	0	0	0	0
Total Investment Income (Loss)	0	0	0	0
Total Revenues	621,251	610,025	1,533,968	1,428,126
Public Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	100,574	79,689	300,152	258,347
Carried Interest	9,900	0	9,900	0
Incentive Fees	18,001	4,074	52,059	8,384
Total Realized Performance Income (Loss)	27,901	4,074	61,959	8,384
Net Realized Gains (Losses)	0	0	0	0
Interest Income and Dividends	0	0	0	0
Total Investment Income (Loss)	0	0	0	0
Total Revenues	128,475	83,763	362,111	266,731
Capital Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	186,498	85,440	398,781	300,235
Carried Interest	0	0	0	0
Incentive Fees	0	0	0	0
Total Realized Performance Income (Loss)	0	0	0	0
Net Realized Gains (Losses)	0	0	0	0
Interest Income and Dividends	0	0	0	0
Total Investment Income (Loss)	0	0	0	0
Total Revenues	186,498	85,440	398,781	300,235
Principal Activities Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Carried Interest	0	0	0	0
Incentive Fees	0	0	0	0
Total Realized Performance Income (Loss)	0	0	0	0
Net Realized Gains (Losses)	181,026	76,053	286,381	162,684
Interest Income and Dividends	61,717	70,557	205,522	195,275
Total Investment Income (Loss)	242,743	146,610	491,903	357,959
Total Revenues	242,743	146,610	491,903	357,959
Management Fees
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	188,866	178,942	547,765	517,393
Management Fees | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	276,595	232,954	789,630	670,807
Management Fees | Private Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	176,071	153,841	490,556	419,606
Management Fees | Public Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	100,524	79,113	299,074	251,201
Management Fees | Capital Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Management Fees | Principal Activities Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Transaction Fees
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	290,404	181,280	619,278	581,410
Transaction Fees | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	289,030	179,167	609,800	578,667
Transaction Fees | Private Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	93,866	82,258	189,122	237,392
Transaction Fees | Public Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	8,666	11,469	21,897	41,040
Transaction Fees | Capital Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	186,498	85,440	398,781	300,235
Transaction Fees | Principal Activities Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Monitoring Fees
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	20,176	14,478	63,125	58,977
Monitoring Fees | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	20,176	14,342	63,100	58,072
Monitoring Fees | Private Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	20,176	14,342	63,100	58,072
Monitoring Fees | Public Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Monitoring Fees | Capital Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Monitoring Fees | Principal Activities Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Fee Credits
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	(73,904)	(70,641)	(137,804)	(207,396)
Fee Credits | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	(82,187)	(70,747)	(178,982)	(211,148)
Fee Credits | Private Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	(73,571)	(59,854)	(158,163)	(177,254)
Fee Credits | Public Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	(8,616)	(10,893)	(20,819)	(33,894)
Fee Credits | Capital Markets Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	0	0	0	0
Fee Credits | Principal Activities Business Line | Reportable segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Fees and Other	$ 0	$ 0	$ 0	$ 0