Commitments and Contingencies - Unfunded Commitments (Details) $ in Millions	Jun. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Unfunded Commitments	$ 2,862.4
Operating Segments | Corporate Private Equity
Segment Reporting Information [Line Items]
Unfunded Commitments	1,385.6
Operating Segments | Real Assets
Segment Reporting Information [Line Items]
Unfunded Commitments	789.4
Operating Segments | Global Market Strategies
Segment Reporting Information [Line Items]
Unfunded Commitments	538.5
Operating Segments | Investment Solutions
Segment Reporting Information [Line Items]
Unfunded Commitments	$ 148.9