INVESTMENTS (Investments of the Consolidated Funds) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) issuer	Dec. 31, 2016 USD ($) issuer
Investments
Number of single issuers above 5% | issuer	0
Single issuer or investor threshold, as a percent	5.00%
Consolidated Funds
Investments
Investments, at fair value	$ 3,405,891	$ 3,330,203
Number of single issuers above 5% | issuer	0	0
Single issuer or investor threshold, as a percent	5.00%	5.00%
Consolidated Funds | Fixed income asset
Investments
Investments, at fair value	$ 2,975,554	$ 2,953,564
Fair value as a percentage of total investments	87.40%	88.80%
Consolidated Funds | Equity securities
Investments
Investments, at fair value	$ 430,337	$ 376,639
Fair value as a percentage of total investments	12.60%	11.20%
Consolidated Funds | United States | Fixed income asset
Investments
Investments, at fair value	$ 1,922,777	$ 1,955,301
Fair value as a percentage of total investments	56.70%	58.70%
Investments, at cost	$ 1,919,405	$ 1,945,977
Consolidated Funds | United States | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 697,226	$ 665,773
Fair value as a percentage of total investments	20.60%	20.00%
Consolidated Funds | United States | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 60,918	$ 64,840
Fair value as a percentage of total investments	1.80%	1.90%
Consolidated Funds | United States | Fixed income asset | Energy
Investments
Investments, at fair value	$ 56,638	$ 45,409
Fair value as a percentage of total investments	1.70%	1.40%
Consolidated Funds | United States | Fixed income asset | Financials
Investments
Investments, at fair value	$ 152,241	$ 139,285
Fair value as a percentage of total investments	4.50%	4.20%
Consolidated Funds | United States | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 230,378	$ 246,403
Fair value as a percentage of total investments	6.80%	7.40%
Consolidated Funds | United States | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 142,002	$ 149,632
Fair value as a percentage of total investments	4.20%	4.50%
Consolidated Funds | United States | Fixed income asset | Information technology
Investments
Investments, at fair value	$ 161,950	$ 194,394
Fair value as a percentage of total investments	4.80%	5.80%
Consolidated Funds | United States | Fixed income asset | Materials
Investments
Investments, at fair value	$ 137,548	$ 139,994
Fair value as a percentage of total investments	4.00%	4.20%
Consolidated Funds | United States | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 255,755	$ 261,771
Fair value as a percentage of total investments	7.50%	7.90%
Consolidated Funds | United States | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 28,121	$ 47,800
Fair value as a percentage of total investments	0.80%	1.40%
Consolidated Funds | United States | Equity securities
Investments
Investments, at fair value	$ 197,134	$ 172,117
Fair value as a percentage of total investments	5.80%	5.20%
Investments, at cost	$ 172,872	$ 149,872
Consolidated Funds | United States | Equity securities | Energy
Investments
Investments, at fair value	$ 444	$ 421
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | United States | Equity securities | Partnership and LLC interests
Investments
Investments, at fair value	$ 196,690	$ 171,696
Fair value as a percentage of total investments	5.80%	5.20%
Consolidated Funds | Europe | Fixed income asset
Investments
Investments, at fair value	$ 950,089	$ 869,474
Fair value as a percentage of total investments	27.80%	26.20%
Investments, at cost	$ 992,614	$ 892,108
Consolidated Funds | Europe | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 314,705	$ 274,678
Fair value as a percentage of total investments	9.20%	8.20%
Consolidated Funds | Europe | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 39,077	$ 39,197
Fair value as a percentage of total investments	1.10%	1.20%
Consolidated Funds | Europe | Fixed income asset | Financials
Investments
Investments, at fair value	$ 39,491	$ 28,769
Fair value as a percentage of total investments	1.20%	0.90%
Consolidated Funds | Europe | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 115,639	$ 111,589
Fair value as a percentage of total investments	3.40%	3.40%
Consolidated Funds | Europe | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 124,818	$ 118,466
Fair value as a percentage of total investments	3.70%	3.60%
Consolidated Funds | Europe | Fixed income asset | Information technology
Investments
Investments, at fair value	$ 37,476	$ 49,507
Fair value as a percentage of total investments	1.10%	1.50%
Consolidated Funds | Europe | Fixed income asset | Materials
Investments
Investments, at fair value	$ 130,887	$ 124,629
Fair value as a percentage of total investments	3.80%	3.70%
Consolidated Funds | Europe | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 136,484	$ 118,632
Fair value as a percentage of total investments	4.00%	3.60%
Consolidated Funds | Europe | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 11,512	$ 4,007
Fair value as a percentage of total investments	0.30%	0.10%
Consolidated Funds | Europe | Equity securities
Investments
Investments, at fair value	$ 43,086	$ 42,870
Fair value as a percentage of total investments	1.20%	1.20%
Investments, at cost	$ 67,266	$ 67,290
Consolidated Funds | Europe | Equity securities | Consumer staples
Investments
Investments, at fair value	$ 1,538	$ 1,517
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Europe | Equity securities | Healthcare, education and childcare
Investments
Investments, at fair value	$ 41,524	$ 41,329
Fair value as a percentage of total investments	1.20%	1.20%
Consolidated Funds | Europe | Equity securities | Telecommunication services
Investments
Investments, at fair value	$ 24	$ 24
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Asia and other | Fixed income asset
Investments
Investments, at fair value	$ 23,400	$ 44,188
Fair value as a percentage of total investments	0.60%	1.30%
Investments, at cost	$ 23,175	$ 46,545
Consolidated Funds | Asia and other | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 15,281	$ 24,244
Fair value as a percentage of total investments	0.40%	0.70%
Consolidated Funds | Asia and other | Fixed income asset | Financials
Investments
Investments, at fair value	$ 0	$ 1,238
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Asia and other | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 0	$ 10,010
Fair value as a percentage of total investments	0.00%	0.30%
Consolidated Funds | Asia and other | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 8,119	$ 8,696
Fair value as a percentage of total investments	0.20%	0.30%
Consolidated Funds | Asia and other | Equity securities
Investments
Investments, at fair value	$ 158,982	$ 143,919
Fair value as a percentage of total investments	4.70%	4.30%
Investments, at cost	$ 122,418	$ 122,418
Consolidated Funds | Asia and other | Equity securities | Consumer discretionary
Investments
Investments, at fair value	$ 47,689	$ 44,642
Fair value as a percentage of total investments	1.40%	1.30%
Consolidated Funds | Asia and other | Equity securities | Consumer staples
Investments
Investments, at fair value	$ 50,078	$ 50,101
Fair value as a percentage of total investments	1.50%	1.50%
Consolidated Funds | Asia and other | Equity securities | Healthcare, education and childcare
Investments
Investments, at fair value	$ 44,637	$ 32,598
Fair value as a percentage of total investments	1.30%	1.00%
Consolidated Funds | Asia and other | Equity securities | Industrials
Investments
Investments, at fair value	$ 16,578	$ 16,578
Fair value as a percentage of total investments	0.50%	0.50%
Consolidated Funds | Canada | Fixed income asset
Investments
Investments, at fair value	$ 48,586	$ 48,848
Fair value as a percentage of total investments	1.40%	1.50%
Investments, at cost	$ 47,982	$ 48,274
Consolidated Funds | Canada | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 1,374	$ 0
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Canada | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 5,205	$ 5,256
Fair value as a percentage of total investments	0.20%	0.20%
Consolidated Funds | Canada | Fixed income asset | Energy
Investments
Investments, at fair value	$ 13,083	$ 12,830
Fair value as a percentage of total investments	0.40%	0.40%
Consolidated Funds | Canada | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 15,233	$ 15,509
Fair value as a percentage of total investments	0.40%	0.50%
Consolidated Funds | Canada | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 1,395	$ 1,401
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Canada | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 12,296	$ 13,852
Fair value as a percentage of total investments	0.40%	0.40%
Consolidated Funds | Canada | Equity securities
Investments
Investments, at fair value	$ 6,160	$ 164
Fair value as a percentage of total investments	0.20%	0.00%
Investments, at cost	$ 17,202	$ 408
Consolidated Funds | Canada | Equity securities | Energy
Investments
Investments, at fair value	$ 6,160	$ 164
Fair value as a percentage of total investments	0.20%	0.00%
Consolidated Funds | Australia | Fixed income asset
Investments
Investments, at fair value	$ 30,702	$ 35,753
Fair value as a percentage of total investments	0.90%	1.10%
Investments, at cost	$ 31,607	$ 37,975
Consolidated Funds | Australia | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 5,461	$ 5,627
Fair value as a percentage of total investments	0.20%	0.20%
Consolidated Funds | Australia | Fixed income asset | Energy
Investments
Investments, at fair value	$ 2,681	$ 6,046
Fair value as a percentage of total investments	0.10%	0.20%
Consolidated Funds | Australia | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 1,450	$ 2,926
Fair value as a percentage of total investments	0.00%	0.10%
Consolidated Funds | Australia | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 21,110	$ 21,154
Fair value as a percentage of total investments	0.60%	0.60%
Consolidated Funds | Australia | Equity securities
Investments
Investments, at fair value	$ 24,975	$ 17,569
Fair value as a percentage of total investments	0.70%	0.50%
Investments, at cost	$ 18,442	$ 18,442
Consolidated Funds | Australia | Equity securities | Utilities
Investments
Investments, at fair value	$ 24,975	$ 17,569
Fair value as a percentage of total investments	0.70%	0.50%