Redeemable Non-Controlling Interests in Consolidated Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	$ 98,460		$ 98,460		$ 104,587
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,434)	2,458	(193)	3,256
Operating Companies [Member]
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	4,800		4,800		6,472
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	301	1,465	594	1,940
Consolidated Funds [Member]
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	93,660		93,660		98,115
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	$ (2,735)	$ 993	$ (787)	$ 1,316