INVESTMENTS - Investments, at Fair Value (Detail) - Consolidated Funds - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Investments In Marketable Securities [Line Items]
Real estate investments, at fair value	$ 230,741	$ 0
Real estate, fair value as a percentage of investments of consolidated funds	3.10%	0.00%
Investments, at fair value	$ 7,358,409	$ 6,531,385
Total investments, fair value as a percentage of investments of consolidated funds	100.00%	100.00%
Securities Sold Short	$ 0	$ (2,609)
Proceeds from securities sold short	0	2,644
Debt securities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 6,995,677	$ 6,502,413
Debt, fair value as a percentage of investments of consolidated funds	95.10%	99.50%
Equity securities
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 131,991	$ 28,972
Equity securities, fair value as a percentage of investments of consolidated funds	1.80%	0.50%
Securities Sold Short	$ 0	$ (2,609)
United States
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities, cost	3,981,956	4,019,823
Equity securities, cost	137,149	6,117
Real estate investments, at fair value	$ 230,741	$ 0
Real estate, fair value as a percentage of investments of consolidated funds	3.10%	0.00%
Real estate, cost	$ 230,741	$ 0
United States | Debt securities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 3,960,403	$ 3,860,665
Debt, fair value as a percentage of investments of consolidated funds	53.90%	59.10%
United States | Debt securities | Communication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 464,356	$ 543,948
Debt, fair value as a percentage of investments of consolidated funds	6.40%	8.40%
United States | Debt securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 508,701	$ 506,551
Debt, fair value as a percentage of investments of consolidated funds	6.90%	7.80%
United States | Debt securities | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 92,102	$ 112,197
Debt, fair value as a percentage of investments of consolidated funds	1.30%	1.70%
United States | Debt securities | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 223,671	$ 204,568
Debt, fair value as a percentage of investments of consolidated funds	3.00%	3.10%
United States | Debt securities | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 355,113	$ 332,240
Debt, fair value as a percentage of investments of consolidated funds	4.80%	5.10%
United States | Debt securities | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 512,864	$ 537,592
Debt, fair value as a percentage of investments of consolidated funds	7.00%	8.20%
United States | Debt securities | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 563,920	$ 443,406
Debt, fair value as a percentage of investments of consolidated funds	7.70%	6.80%
United States | Debt securities | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 524,390	$ 536,000
Debt, fair value as a percentage of investments of consolidated funds	7.10%	8.20%
United States | Debt securities | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 294,300	$ 289,499
Debt, fair value as a percentage of investments of consolidated funds	4.00%	4.40%
United States | Debt securities | Real estate
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 204,933	$ 217,633
Debt, fair value as a percentage of investments of consolidated funds	2.80%	3.30%
United States | Debt securities | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 216,053	$ 137,031
Debt, fair value as a percentage of investments of consolidated funds	2.90%	2.10%
United States | Equity securities
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 131,897	$ 5,426
Equity securities, fair value as a percentage of investments of consolidated funds	1.80%	0.10%
United States | Equity securities | Communication services
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 312	$ 0
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
United States | Equity securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 658	$ 1,915
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.10%
United States | Equity securities | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 256	$ 131
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
United States | Equity securities | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 837
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
United States | Equity securities | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 1,348
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
United States | Equity securities | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 88
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
United States | Equity securities | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 130,671	$ 1,107
Equity securities, fair value as a percentage of investments of consolidated funds	1.80%	0.00%
Europe
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities, cost	$ 2,876,531	$ 2,477,821
Equity securities, cost	1,227	320
Europe | Debt securities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 2,870,174	$ 2,413,280
Debt, fair value as a percentage of investments of consolidated funds	39.00%	36.90%
Europe | Debt securities | Communication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 469,822	$ 530,337
Debt, fair value as a percentage of investments of consolidated funds	6.40%	8.10%
Europe | Debt securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 659,001	$ 545,324
Debt, fair value as a percentage of investments of consolidated funds	9.00%	8.30%
Europe | Debt securities | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 178,609	$ 160,406
Debt, fair value as a percentage of investments of consolidated funds	2.40%	2.50%
Europe | Debt securities | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 11,316	$ 15,260
Debt, fair value as a percentage of investments of consolidated funds	0.20%	0.20%
Europe | Debt securities | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 101,933	$ 48,545
Debt, fair value as a percentage of investments of consolidated funds	1.40%	0.70%
Europe | Debt securities | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 579,765	$ 418,516
Debt, fair value as a percentage of investments of consolidated funds	7.90%	6.40%
Europe | Debt securities | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 362,120	$ 246,640
Debt, fair value as a percentage of investments of consolidated funds	4.90%	3.80%
Europe | Debt securities | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 177,152	$ 194,988
Debt, fair value as a percentage of investments of consolidated funds	2.40%	3.00%
Europe | Debt securities | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 230,289	$ 221,660
Debt, fair value as a percentage of investments of consolidated funds	3.10%	3.40%
Europe | Debt securities | Real estate
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 96,315	$ 30,045
Debt, fair value as a percentage of investments of consolidated funds	1.30%	0.50%
Europe | Debt securities | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 3,852	$ 1,559
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.00%
Europe | Equity securities
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 94	$ 986
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.10%
Europe | Equity securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 94	$ 0
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%
Europe | Equity securities | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 38
Equity securities, fair value as a percentage of investments of consolidated funds		0.00%
Europe | Equity securities | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	0	$ 948
Equity securities, fair value as a percentage of investments of consolidated funds		0.10%
Asia and other
Schedule Of Investments In Marketable Securities [Line Items]
Debt securities, cost	164,650	$ 233,603
Equity securities, cost	0	22,977
Asia and other | Debt securities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 165,100	$ 228,468
Debt, fair value as a percentage of investments of consolidated funds	2.20%	3.50%
Asia and other | Debt securities | Communication services
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 15,750	$ 12,069
Debt, fair value as a percentage of investments of consolidated funds	0.20%	0.20%
Asia and other | Debt securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 40,073	$ 36,822
Debt, fair value as a percentage of investments of consolidated funds	0.50%	0.60%
Asia and other | Debt securities | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 11,545	$ 11,867
Debt, fair value as a percentage of investments of consolidated funds	0.20%	0.20%
Asia and other | Debt securities | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 13,471	$ 20,594
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.30%
Asia and other | Debt securities | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 10,313	$ 13,995
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.20%
Asia and other | Debt securities | Government
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 917	$ 12,155
Debt, fair value as a percentage of investments of consolidated funds	0.00%	0.20%
Asia and other | Debt securities | Health care
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 8,923	$ 9,633
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.10%
Asia and other | Debt securities | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 31,814	$ 40,468
Debt, fair value as a percentage of investments of consolidated funds	0.40%	0.70%
Asia and other | Debt securities | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 5,639	$ 1,887
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.00%
Asia and other | Debt securities | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 5,604	$ 15,516
Debt, fair value as a percentage of investments of consolidated funds	0.10%	0.20%
Asia and other | Debt securities | Real estate
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 751	$ 38,592
Debt, fair value as a percentage of investments of consolidated funds	0.00%	0.60%
Asia and other | Debt securities | Utilities
Schedule Of Investments In Marketable Securities [Line Items]
Debt, fair value	$ 20,300	$ 14,870
Debt, fair value as a percentage of investments of consolidated funds	0.30%	0.20%
Asia and other | Equity securities
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 22,560
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.30%
Asia and other | Equity securities | Consumer discretionary
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 874
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
Asia and other | Equity securities | Consumer staples
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 997
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
Asia and other | Equity securities | Energy
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 382
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
Asia and other | Equity securities | Financials
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 2,935
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
Asia and other | Equity securities | Industrials
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 11,265
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.20%
Asia and other | Equity securities | Information technology
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 1,725
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.00%
Asia and other | Equity securities | Materials
Schedule Of Investments In Marketable Securities [Line Items]
Equity securities, fair value	$ 0	$ 4,382
Equity securities, fair value as a percentage of investments of consolidated funds	0.00%	0.10%