Redeemable Non-Controlling Interests in Consolidated Subsidiaries (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	$ 81,031		$ 85,703
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	3,495	2,241
Operating Companies
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	5,971		4,106
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	1,795	293
Consolidated Funds
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries	75,060		81,597
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	$ 1,700	$ 1,948