Investments, at Fair Value (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net gains (losses) from investment activities of consolidated funds
Net realized gain (loss) on investments	$ 733,521	$ 513,583	$ 1,807,659	$ 1,273,844
Net change in unrealized appreciation (depreciation) on investments	(180,216)	(737,362)	625,607	(58,734)
Investments and Other Financial Instruments [Member]
Net gains (losses) from investment activities of consolidated funds
Net realized gain (loss) on investments	726,150	435,759	1,726,808	1,603,817
Net change in unrealized appreciation (depreciation) on investments	(302,518)	(600,415)	587,203	(53,202)
Total return and credit default swaps [Member]
Net gains (losses) from investment activities of consolidated funds
Net realized gain (loss) on investments	19,538	7,382	30,464	12,727
Net change in unrealized appreciation (depreciation) on investments	18,938	(4,710)	36,122	20,953
Forward contracts (net) [Member]
Net gains (losses) from investment activities of consolidated funds
Net realized gain (loss) on investments	(1,913)	72,764	62,904	(338,613)
Net change in unrealized appreciation (depreciation) on investments	98,624	(122,643)	(2,194)	10,442
Options and futures [Member]
Net gains (losses) from investment activities of consolidated funds
Net realized gain (loss) on investments	(10,254)	(2,322)	(12,517)	(4,087)
Net change in unrealized appreciation (depreciation) on investments	$ 4,740	$ (9,594)	$ 4,476	$ (36,927)