Investments of Operating Entities and Consolidated Funds - Variable Interest Entities (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total assets of nonconsolidated variable interest entities	$ 5,100.0	$ 3,100.0
Total liabilities of nonconsolidated variable interest entities	700.0	473.3
Maximum exposure regarding nonconsolidated variable interest entities	$ 483.9	$ 327.8