Variable Interest Entities (Non-Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	$ 235.2	$ 360.2
Maximum Exposure to Loss	1,685.3	1,795.2
Total VIE Assets	7,135.8	8,747.4
Collateralized Loan Obligations [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	82.7	134.0
Maximum Exposure to Loss	768.8	926.9
Total VIE Assets	6,409.1	7,737.1
Consumer Loan Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	123.4	170.6
Maximum Exposure to Loss	867.0	797.8
Total VIE Assets	602.1	485.2
Asset Management Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	3.6	11.3
Maximum Exposure to Loss	3.6	11.3
Total VIE Assets	49.8	432.3
Private Equity Vehicles [Member]
Variable Interest Entity [Line Items]
Total Financial Statement Carrying Amount, Assets	25.5	44.3
Maximum Exposure to Loss	45.9	59.2
Total VIE Assets	$ 74.8	$ 92.8