Variable Interest Entities (Non-Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	$ 286.8	$ 360.2
Maximum Exposure to Loss	1,545.9	1,795.2
Total VIE Assets	6,389.8	8,747.4
Collateralized Loan Obligations [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	84.6	134.0
Maximum Exposure to Loss	373.9	926.9
Total VIE Assets	5,659.6	7,737.1
Consumer Loan Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	171.0	170.6
Maximum Exposure to Loss	1,116.2	797.8
Total VIE Assets	609.2	485.2
Asset Management Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	6.9	11.3
Maximum Exposure to Loss	6.9	11.3
Total VIE Assets	49.0	432.3
Private Equity Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	24.3	44.3
Maximum Exposure to Loss	48.9	59.2
Total VIE Assets	$ 72.0	$ 92.8