INVESTMENTS - By Sector (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($) item	Dec. 31, 2015 USD ($) item
Investments
Single issuer or investor threshold, as a percent	5.00%	5.00%
Consolidated Funds
Investments
Investments, at fair value	$ 2,529,173	$ 2,559,783
Number of single issuers above 5% | item	0	0
Consolidated Funds | Fixed income asset
Investments
Investments, at fair value	$ 2,322,843	$ 2,338,024
Fair value as a percentage of total investments	91.90%	91.20%
Consolidated Funds | Equity securities
Investments
Investments, at fair value	$ 206,330	$ 221,759
Fair value as a percentage of total investments	8.10%	8.80%
Consolidated Funds | United States | Fixed income asset
Investments
Investments, at fair value	$ 1,488,141	$ 1,411,220
Fair value as a percentage of total investments	59.10%	55.10%
Investments, at cost	$ 1,504,932	$ 1,462,570
Consolidated Funds | United States | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 407,161	$ 393,902
Fair value as a percentage of total investments	16.20%	15.40%
Consolidated Funds | United States | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 45,017	$ 40,030
Fair value as a percentage of total investments	1.80%	1.60%
Consolidated Funds | United States | Fixed income asset | Energy
Investments
Investments, at fair value	$ 46,341	$ 38,617
Fair value as a percentage of total investments	1.80%	1.50%
Consolidated Funds | United States | Fixed income asset | Financials
Investments
Investments, at fair value	$ 75,041	$ 78,806
Fair value as a percentage of total investments	3.00%	3.10%
Consolidated Funds | United States | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 171,475	$ 162,191
Fair value as a percentage of total investments	6.80%	6.30%
Consolidated Funds | United States | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 151,775	$ 161,830
Fair value as a percentage of total investments	6.00%	6.30%
Consolidated Funds | United States | Fixed income asset | Information technology
Investments
Investments, at fair value	$ 172,128	$ 138,186
Fair value as a percentage of total investments	6.80%	5.40%
Consolidated Funds | United States | Fixed income asset | Materials
Investments
Investments, at fair value	$ 97,395	$ 95,767
Fair value as a percentage of total investments	3.90%	3.70%
Consolidated Funds | United States | Fixed income asset | Partnership interests
Investments
Investments, at fair value	$ 115,440	$ 86,902
Fair value as a percentage of total investments	4.60%	3.40%
Consolidated Funds | United States | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 176,548	$ 202,256
Fair value as a percentage of total investments	7.00%	7.90%
Consolidated Funds | United States | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 29,820	$ 12,733
Fair value as a percentage of total investments	1.20%	0.50%
Consolidated Funds | United States | Equity securities
Investments
Investments, at fair value	$ 630	$ 854
Fair value as a percentage of total investments	0.00%	0.00%
Investments, at cost	$ 5,620	$ 8,304
Consolidated Funds | United States | Equity securities | Healthcare, education and childcare
Investments
Investments, at fair value	$ 344	$ 344
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | United States | Equity securities | Telecommunication services
Investments
Investments, at fair value	$ 286	$ 510
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Europe | Fixed income asset
Investments
Investments, at fair value	$ 719,675	$ 796,621
Fair value as a percentage of total investments	28.40%	31.10%
Investments, at cost	$ 765,916	$ 836,217
Consolidated Funds | Europe | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 170,248	$ 221,707
Fair value as a percentage of total investments	6.70%	8.70%
Consolidated Funds | Europe | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 48,278	$ 50,625
Fair value as a percentage of total investments	1.90%	2.00%
Consolidated Funds | Europe | Fixed income asset | Financials
Investments
Investments, at fair value	$ 27,256	$ 29,922
Fair value as a percentage of total investments	1.10%	1.20%
Consolidated Funds | Europe | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 104,814	$ 104,704
Fair value as a percentage of total investments	4.10%	4.10%
Consolidated Funds | Europe | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 104,005	$ 109,778
Fair value as a percentage of total investments	4.10%	4.30%
Consolidated Funds | Europe | Fixed income asset | Information technology
Investments
Investments, at fair value	$ 32,944	$ 31,562
Fair value as a percentage of total investments	1.30%	1.20%
Consolidated Funds | Europe | Fixed income asset | Materials
Investments
Investments, at fair value	$ 103,071	$ 98,450
Fair value as a percentage of total investments	4.10%	3.80%
Consolidated Funds | Europe | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 128,271	$ 149,105
Fair value as a percentage of total investments	5.10%	5.80%
Consolidated Funds | Europe | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 788	$ 768
Fair value as a percentage of total investments	0.00%	0.00%
Consolidated Funds | Europe | Equity securities
Investments
Investments, at fair value	$ 59,374	$ 43,045
Fair value as a percentage of total investments	2.40%	1.80%
Investments, at cost	$ 89,778	$ 80,827
Consolidated Funds | Europe | Equity securities | Consumer discretionary
Investments
Investments, at fair value	$ 3,872	$ 4,306
Fair value as a percentage of total investments	0.20%	0.20%
Consolidated Funds | Europe | Equity securities | Consumer staples
Investments
Investments, at fair value	$ 1,415	$ 1,286
Fair value as a percentage of total investments	0.10%	0.10%
Consolidated Funds | Europe | Equity securities | Healthcare, education and childcare
Investments
Investments, at fair value	$ 54,064	$ 37,294
Fair value as a percentage of total investments	2.10%	1.50%
Consolidated Funds | Europe | Equity securities | Telecommunication services
Investments
Investments, at fair value	$ 23	$ 159
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	$ 45,923	$ 68,718
Fair value as a percentage of total investments	1.70%	2.70%
Investments, at cost	$ 47,987	$ 57,868
Consolidated Funds | Asia and other | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 25,541	$ 34,810
Fair value as a percentage of total investments	1.00%	1.40%
Consolidated Funds | Asia and other | Fixed income asset | Financials
Investments
Investments, at fair value	$ 1,236
Fair value as a percentage of total investments	0.00%
Consolidated Funds | Asia and other | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 10,440	$ 23,999
Fair value as a percentage of total investments	0.40%	0.90%
Consolidated Funds | Asia and other | Fixed income asset | Telecommunication services
Investments
Investments, at fair value	$ 8,706	$ 9,909
Fair value as a percentage of total investments	0.30%	0.40%
Consolidated Funds | Asia and other | Equity securities
Investments
Investments, at fair value	$ 125,536	$ 156,730
Fair value as a percentage of total investments	4.90%	6.20%
Investments, at cost	$ 118,730	$ 118,730
Consolidated Funds | Asia and other | Equity securities | Consumer discretionary
Investments
Investments, at fair value	$ 31,600	$ 55,532
Fair value as a percentage of total investments	1.20%	2.20%
Consolidated Funds | Asia and other | Equity securities | Consumer staples
Investments
Investments, at fair value	$ 48,447	$ 55,442
Fair value as a percentage of total investments	1.90%	2.20%
Consolidated Funds | Asia and other | Equity securities | Healthcare, education and childcare
Investments
Investments, at fair value	$ 32,598	$ 32,865
Fair value as a percentage of total investments	1.30%	1.30%
Consolidated Funds | Asia and other | Equity securities | Industrials
Investments
Investments, at fair value	$ 12,891	$ 12,891
Fair value as a percentage of total investments	0.50%	0.50%
Consolidated Funds | Canada | Fixed income asset
Investments
Investments, at fair value	$ 39,687	$ 32,879
Fair value as a percentage of total investments	1.60%	1.30%
Investments, at cost	$ 40,534	$ 34,397
Consolidated Funds | Canada | Fixed income asset | Consumer discretionary
Investments
Investments, at fair value	$ 1,414	$ 827
Fair value as a percentage of total investments	0.10%	0.00%
Consolidated Funds | Canada | Fixed income asset | Consumer staples
Investments
Investments, at fair value	$ 3,987	$ 1,369
Fair value as a percentage of total investments	0.20%	0.10%
Consolidated Funds | Canada | Fixed income asset | Energy
Investments
Investments, at fair value	$ 7,199	$ 8,724
Fair value as a percentage of total investments	0.30%	0.30%
Consolidated Funds | Canada | Fixed income asset | Healthcare, education and childcare
Investments
Investments, at fair value	$ 12,969	$ 14,819
Fair value as a percentage of total investments	0.50%	0.60%
Consolidated Funds | Canada | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 631	$ 513
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	$ 13,487	$ 6,627
Fair value as a percentage of total investments	0.50%	0.30%
Consolidated Funds | Canada | Equity securities
Investments
Investments, at fair value	$ 413
Investments, at cost	408	$ 0
Consolidated Funds | Canada | Equity securities | Consumer discretionary
Investments
Investments, at fair value	413
Consolidated Funds | Australia | Fixed income asset
Investments
Investments, at fair value	$ 29,417	$ 28,586
Fair value as a percentage of total investments	1.10%	1.00%
Investments, at cost	$ 36,827	$ 39,574
Consolidated Funds | Australia | Fixed income asset | Energy
Investments
Investments, at fair value	$ 8,827	$ 8,888
Fair value as a percentage of total investments	0.30%	0.30%
Consolidated Funds | Australia | Fixed income asset | Industrials
Investments
Investments, at fair value	$ 4,635	$ 3,657
Fair value as a percentage of total investments	0.20%	0.10%
Consolidated Funds | Australia | Fixed income asset | Utilities
Investments
Investments, at fair value	$ 15,955	$ 16,041
Fair value as a percentage of total investments	0.60%	0.60%
Consolidated Funds | Australia | Equity securities
Investments
Investments, at fair value	$ 20,377	$ 21,130
Fair value as a percentage of total investments	0.80%	0.80%
Investments, at cost	$ 23,693	$ 25,524
Consolidated Funds | Australia | Equity securities | Telecommunication services
Investments
Investments, at fair value	$ 2,242	$ 5,370
Fair value as a percentage of total investments	0.10%	0.20%
Consolidated Funds | Australia | Equity securities | Utilities
Investments
Investments, at fair value	$ 18,135	$ 15,760
Fair value as a percentage of total investments	0.70%	0.60%