Investments - Components of Interest and Other Income of Consolidated Funds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Method Investments and Joint Ventures [Abstract]
Interest income from investments	$ 873.1	$ 864.9	$ 876.8
Other income	102.4	91.1	166.3
Total	$ 975.5	$ 956.0	$ 1,043.1