Redeemable Non-Controlling Interests in Consolidated Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	$ 88,011		$ 88,011		$ 104,587
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	(1,033)	(783)	(1,225)	2,473
Operating Companies [Member]
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	5,148		5,148		6,472
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	298	1,147	893	3,087
Consolidated Funds [Member]
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	82,863		82,863		98,115
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	$ (1,331)	$ (1,930)	$ (2,118)	$ (614)