INVESTMENTS - Fair Value (Details) - Consolidated Funds - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 4,503,053	$ 3,672,118
Equity securities:	$ 236,633	$ 136,116
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	95.00%	96.40%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	5.00%	3.60%
Investments, at fair value	$ 4,739,686	$ 3,808,234
Total investments, at fair value, Fair Value as a Percentage of Investments of Consolidated Funds	100.00%	100.00%
Total securities sold short, at fair value	$ (81,086)	$ (41,016)
Equity securities:
Schedule Of Investments In Marketable Securities [Line Items]
Total securities sold short, at fair value	(81,086)	(41,016)
United States:
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	3,023,186	2,392,717
Equity securities:	$ 9,749	$ 7,725
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	63.80%	62.90%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.20%	0.20%
United States: | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 688,630	$ 628,621
Equity securities:	$ 735	$ 711
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	14.50%	16.50%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 105,482	$ 123,395
Equity securities:	$ 209	$ 0
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	2.20%	3.20%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 80,016	$ 55,655
Equity securities:	$ 1,845	$ 2,002
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	1.70%	1.50%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
United States: | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 286,549	$ 182,685
Equity securities:	$ 5,881	$ 3,977
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	6.10%	4.80%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
United States: | Government
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 5,827	$ 5,234
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
United States: | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 433,737	$ 337,138
Equity securities:	$ 305	$ 343
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	9.20%	8.90%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 442,309	$ 379,122
Equity securities:	$ 326	$ 1
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	9.40%	10.00%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 426,966	$ 272,637
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	9.00%	7.20%
United States: | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 266,851	$ 237,417
Equity securities:	$ 167	$ 691
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	5.60%	6.20%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Telecommunication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 167,012	$ 93,893
Equity securities:	$ 281	$ 0
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	3.50%	2.50%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
United States: | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 119,807	$ 76,920
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	2.50%	2.00%
Europe:
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 1,401,955	$ 1,226,100
Equity securities:	$ 2,730	$ 1,605
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	29.60%	32.10%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.00%
Europe: | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 447,928	$ 374,627
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	9.50%	9.80%
Europe: | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 120,491	$ 92,750
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	2.50%	2.40%
Europe: | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 2,400	$ 13,274
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.30%
Europe: | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 17,239	$ 13,822
Equity securities:	$ 2,730	$ 1,605
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.40%	0.40%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.00%
Europe: | Government
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 3,381	$ 1,996
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
Europe: | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 248,510	$ 210,078
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	5.20%	5.50%
Europe: | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 70,524	$ 54,578
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	1.50%	1.40%
Europe: | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 38,683	$ 23,832
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.80%	0.60%
Europe: | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 255,943	$ 226,961
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	5.40%	6.00%
Europe: | Telecommunication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 195,500	$ 214,182
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	4.10%	5.60%
Europe: | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 1,356	$ 0
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
Asia and other:
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 77,912	$ 53,301
Equity securities:	$ 224,154	$ 126,786
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	1.60%	1.40%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	4.70%	3.40%
Asia and other: | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 23,605	$ 3,145
Equity securities:	$ 13,510	$ 7,639
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.40%	0.10%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.30%	0.20%
Asia and other: | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 750	$ 5,994
Equity securities:	$ 4,910	$ 3,786
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.20%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
Asia and other: | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 7,297	$ 9,570
Equity securities:	$ 6,756	$ 6,978
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.20%	0.30%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.20%
Asia and other: | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 2,519	$ 0
Equity securities:	$ 88,825	$ 44,328
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.00%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	1.90%	1.20%
Asia and other: | Government
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 1,003	$ 1,506
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
Asia and other: | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 14,039	$ 1,245
Equity securities:	$ 414	$ 0
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.30%	0.00%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
Asia and other: | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 11,233	$ 15,450
Equity securities:	$ 42,508	$ 21,564
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.20%	0.40%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.90%	0.60%
Asia and other: | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 443	$ 409
Equity securities:	$ 15,585	$ 16,642
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.30%	0.40%
Asia and other: | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 7,770	$ 10,245
Equity securities:	$ 45,674	$ 19,697
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.20%	0.30%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.90%	0.50%
Asia and other: | Telecommunication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 9,253	$ 4,809
Equity securities:	$ 2,971	$ 4,296
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.20%	0.10%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%
Asia and other: | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities:	$ 0	$ 928
Equity securities:	$ 3,001	$ 1,856
Debt securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.00%	0.00%
Equity securities: Fair Value as a Percentage of Investments of Consolidated Funds	0.10%	0.10%