INVESTMENTS IN AFFILIATES (Detail) - Schedule of Equity investment in investment fund affiliates and equity in net income (loss) from such affiliates (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	$ 1,052,729		$ 1,127,181
Equity in net income (loss) in investment fund affiliates	103,039		172,474		139,347
Arbitrage Alternative Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	123,969	[1]	156,511	[1]
Equity in net income (loss) in investment fund affiliates	1,291	[1]	9,477	[1]
Weighted average percentage ownership in equity investment fund affiliates	3.40%	[1]	4.10%	[1]
Estimated net assets in investment fund affiliates	3,678,904	[1],[2]	3,797,962	[1],[2]
Directional Alternative Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	217,779	[1]	166,644	[1]
Equity in net income (loss) in investment fund affiliates	9,154	[1]	5,972	[1]
Weighted average percentage ownership in equity investment fund affiliates	6.00%	[1]	5.90%	[1]
Estimated net assets in investment fund affiliates	3,619,272	[1],[2]	2,819,306	[1],[2]
Event Driven Alternative Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	229,956	[1]	261,252	[1]
Equity in net income (loss) in investment fund affiliates	(60)	[1]	7,605	[1]
Weighted average percentage ownership in equity investment fund affiliates	3.10%	[1]	2.50%	[1]
Estimated net assets in investment fund affiliates	7,472,680	[1],[2]	10,267,525	[1],[2]
Multi Style Alternative Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	425	[1]	787	[1]
Equity in net income (loss) in investment fund affiliates	(9)	[1]	30	[1]
Weighted average percentage ownership in equity investment fund affiliates	17.60%	[1]	8.10%	[1]
Estimated net assets in investment fund affiliates	2,410	[1],[2]	9,688	[1],[2]
Alternative Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	572,129	[1]	585,194	[1]
Equity in net income (loss) in investment fund affiliates	10,376	[1]	23,084	[1]
Weighted average percentage ownership in equity investment fund affiliates	3.90%	[1]	3.50%	[1]
Estimated net assets in investment fund affiliates	14,773,266	[1],[2]	16,894,481	[1],[2]
Investment Fund Affiliates [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	768,851		829,059
Equity in net income (loss) in investment fund affiliates	26,253		51,102
Weighted average percentage ownership in equity investment fund affiliates	4.10%		3.90%
Estimated net assets in investment fund affiliates	18,593,763	[2]	21,302,670	[2]
Private Equity Funds [Member]
Alternative Funds (1):
Carrying value of Equity method investments, investment fund affiliates	196,722	[1]	243,865	[1]
Equity in net income (loss) in investment fund affiliates	15,877	[1]	28,018	[1]
Weighted average percentage ownership in equity investment fund affiliates	5.10%	[1]	5.50%	[1]
Estimated net assets in investment fund affiliates	$ 3,820,497	[1],[2]	$ 4,408,189	[1],[2]

[1] The Company generally records its alternative fund affiliates on a one month lag and its private equity fund affiliates on a one quarter lag.

[2] Total estimated net assets are generally as at November 30 and September 30, respectively.