Investments of Operating Entities and Consolidated Funds Variable Interest Entities (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entity [Line Items]
Total assets of nonconsolidated variable interest entities	$ 1,400,000,000	$ 1,400,000,000
Total liabilities of nonconsolidated variable interest entities	214,400,000	22,800,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Maximum exposure regarding nonconsolidated variable interest entities	$ 207,200,000	$ 220,900,000