Investments of Operating Entities and Consolidated Funds Variable Interest Entities (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Total assets of nonconsolidated variable interest entities	$ 1,400,000,000	$ 800,000,000
Total liabilities of nonconsolidated variable interest entities	22,800,000	66,100,000
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Maximum exposure regarding nonconsolidated variable interest entities	$ 220,900,000	$ 250,900,000