FAIR VALUE MEASUREMENTS - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Marshall Wace
Liabilities, at fair value:
Entity interests acquired, option to increase, potential interest in acquiree (as a percent)	39.90%
Fair value measured on recurring basis
Assets, at fair value:
Total Investments	$ 37,299,937	$ 32,941,871
Total Assets	37,443,995	33,123,529
Liabilities, at fair value:
Securities Sold Short	513,442	692,007
Unfunded Revolver Commitments	45,170	17,629
Total Liabilities	13,346,978	16,626,181
Fair value measured on recurring basis | Debt Obligations of Consolidated CFEs
Liabilities, at fair value:
Total Liabilities	12,645,610	15,586,216
Fair value measured on recurring basis | Foreign Exchange Forward Contracts
Assets, at fair value:
Total Assets	98,748	96,584
Liabilities, at fair value:
Total Liabilities	102,018	260,948
Fair value measured on recurring basis | Other Derivatives
Assets, at fair value:
Total Assets	45,310	85,074
Liabilities, at fair value:
Total Liabilities	40,738	69,381
Fair value measured on recurring basis | Private Equity
Assets, at fair value:
Total Investments	7,517,830	3,301,261
Fair value measured on recurring basis | Credit
Assets, at fair value:
Total Investments	8,627,571	7,621,320
Fair value measured on recurring basis | Investments of Consolidated CFEs
Assets, at fair value:
Total Investments	13,293,505	15,573,203
Fair value measured on recurring basis | Real Assets
Assets, at fair value:
Total Investments	3,279,482	2,302,061
Fair value measured on recurring basis | Equity Method - Other
Assets, at fair value:
Total Investments	1,744,961	1,384,739
Fair value measured on recurring basis | Other Investments
Assets, at fair value:
Total Investments	2,836,588	2,759,287
Fair value measured on recurring basis | Level I
Assets, at fair value:
Total Investments	2,474,326	2,019,338
Total Assets	2,474,326	2,019,338
Liabilities, at fair value:
Securities Sold Short	513,442	692,007
Unfunded Revolver Commitments	0	0
Total Liabilities	513,442	692,007
Fair value measured on recurring basis | Level I | Debt Obligations of Consolidated CFEs
Liabilities, at fair value:
Total Liabilities	0	0
Fair value measured on recurring basis | Level I | Foreign Exchange Forward Contracts
Assets, at fair value:
Total Assets	0	0
Liabilities, at fair value:
Total Liabilities	0	0
Fair value measured on recurring basis | Level I | Other Derivatives
Assets, at fair value:
Total Assets	0	0
Liabilities, at fair value:
Total Liabilities	0	0
Fair value measured on recurring basis | Level I | Private Equity
Assets, at fair value:
Total Investments	1,284,468	1,043,390
Fair value measured on recurring basis | Level I | Credit
Assets, at fair value:
Total Investments	0	0
Fair value measured on recurring basis | Level I | Investments of Consolidated CFEs
Assets, at fair value:
Total Investments	0	0
Fair value measured on recurring basis | Level I | Real Assets
Assets, at fair value:
Total Investments	0	50,794
Fair value measured on recurring basis | Level I | Equity Method - Other
Assets, at fair value:
Total Investments	294,171	60,282
Fair value measured on recurring basis | Level I | Other Investments
Assets, at fair value:
Total Investments	895,687	864,872
Fair value measured on recurring basis | Level II
Assets, at fair value:
Total Investments	14,916,114	13,170,229
Total Assets	15,024,863	13,299,938
Liabilities, at fair value:
Securities Sold Short	0	0
Unfunded Revolver Commitments	0	0
Total Liabilities	11,677,559	10,636,509
Fair value measured on recurring basis | Level II | Debt Obligations of Consolidated CFEs
Liabilities, at fair value:
Total Liabilities	11,562,503	10,347,980
Fair value measured on recurring basis | Level II | Foreign Exchange Forward Contracts
Assets, at fair value:
Total Assets	98,748	96,584
Liabilities, at fair value:
Total Liabilities	102,018	260,948
Fair value measured on recurring basis | Level II | Other Derivatives
Assets, at fair value:
Total Assets	10,001	33,125
Liabilities, at fair value:
Total Liabilities	13,038	27,581
Fair value measured on recurring basis | Level II | Private Equity
Assets, at fair value:
Total Investments	309,134	85,581
Fair value measured on recurring basis | Level II | Credit
Assets, at fair value:
Total Investments	2,175,830	2,482,383
Fair value measured on recurring basis | Level II | Investments of Consolidated CFEs
Assets, at fair value:
Total Investments	12,197,431	10,220,113
Fair value measured on recurring basis | Level II | Real Assets
Assets, at fair value:
Total Investments	0	0
Fair value measured on recurring basis | Level II | Equity Method - Other
Assets, at fair value:
Total Investments	47,938	247,748
Fair value measured on recurring basis | Level II | Other Investments
Assets, at fair value:
Total Investments	185,781	134,404
Fair value measured on recurring basis | Level III
Assets, at fair value:
Total Investments	19,909,497	17,752,304
Total Assets	19,944,806	17,804,253
Liabilities, at fair value:
Securities Sold Short	0	0
Unfunded Revolver Commitments	45,170	17,629
Total Liabilities	1,155,977	5,297,665
Fair value measured on recurring basis | Level III | Debt Obligations of Consolidated CFEs
Liabilities, at fair value:
Total Liabilities	1,083,107	5,238,236
Fair value measured on recurring basis | Level III | Foreign Exchange Forward Contracts
Assets, at fair value:
Total Assets	0	0
Liabilities, at fair value:
Total Liabilities	0	0
Fair value measured on recurring basis | Level III | Other Derivatives
Assets, at fair value:
Total Assets	35,309	51,949
Liabilities, at fair value:
Total Liabilities	27,700	41,800
Fair value measured on recurring basis | Level III | Private Equity
Assets, at fair value:
Total Investments	5,924,228	2,172,290
Fair value measured on recurring basis | Level III | Credit
Assets, at fair value:
Total Investments	6,451,741	5,138,937
Fair value measured on recurring basis | Level III | Investments of Consolidated CFEs
Assets, at fair value:
Total Investments	1,096,074	5,353,090
Fair value measured on recurring basis | Level III | Real Assets
Assets, at fair value:
Total Investments	3,279,482	2,251,267
Fair value measured on recurring basis | Level III | Equity Method - Other
Assets, at fair value:
Total Investments	1,402,852	1,076,709
Fair value measured on recurring basis | Level III | Other Investments
Assets, at fair value:
Total Investments	$ 1,755,120	$ 1,760,011