Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Schedule of Investments [Line Items]
Equity method investments	$ 960.7	$ 876.6
Operating Segments | Corporate Private Equity
Schedule of Investments [Line Items]
Equity method investments	285.3	254.5
Operating Segments | Global Market Strategies
Schedule of Investments [Line Items]
Equity method investments	24.6	26.7
Operating Segments | Real Assets
Schedule of Investments [Line Items]
Equity method investments	625.7	592.7
Operating Segments | Investment Solutions
Schedule of Investments [Line Items]
Equity method investments	$ 25.1	$ 2.7