Consolidated Investment Products (Fair Value Hierarchy Levels Of Investments Held And Notes Issued By Consolidated Investment Products) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Investments Of Consolidated Investment Products	$ 3,639.4	$ 6,016.1
Fair Value, Inputs, Level 1 [Member]
Investments Of Consolidated Investment Products	167.4	7.7
Significant Other Observable Inputs (Level 2) [Member]
Investments Of Consolidated Investment Products	3,419.5	5,251.6
Significant Unobservable Inputs (Level 3) [Member]
Investments Of Consolidated Investment Products	0.0	388.6
Corporate Debt Securities [Member]
CLO Collateral Assets	3,014.4
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
CLO Collateral Assets	0.0
Corporate Debt Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	3,014.4
Corporate Debt Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0.0
Bank Loans [Member]
CLO Collateral Assets		5,179.6
Bank Loans [Member] | Fair Value, Inputs, Level 1 [Member]
CLO Collateral Assets		0.0
Bank Loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets		5,179.6
Bank Loans [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets		0.0
Bonds [Member]
CLO Collateral Assets	400.8	71.1
Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
CLO Collateral Assets	0.0	0.0
Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	400.8	71.1
Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0.0	0.0
Equity Securities [Member]
CLO Collateral Assets	134.5	0.9
Private Equity Fund Assets	37.2	364.6
Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
CLO Collateral Assets	130.2	0.0
Private Equity Fund Assets	37.2	7.7
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	4.3	0.9
Private Equity Fund Assets	0.0	0.0
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0.0	0.0
Private Equity Fund Assets	0.0	356.9
Debt Securities [Member]
Investments, Fair Value Disclosure		31.7
Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Investments, Fair Value Disclosure		0.0
Debt Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments, Fair Value Disclosure		0.0
Debt Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments, Fair Value Disclosure		31.7
Private Equity Funds [Member]
Private Equity Fund Assets	52.5	368.2
Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Private Equity Fund Assets	0.0	0.0
Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Private Equity Fund Assets	0.0	0.0
Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Private Equity Fund Assets	0.0	0.0
Investments Measured at NAV [Member]
Investments Of Consolidated Investment Products	52.5	368.2
Investments Measured at NAV [Member] | Corporate Debt Securities [Member]
CLO Collateral Assets	0.0
Investments Measured at NAV [Member] | Bank Loans [Member]
CLO Collateral Assets		0.0
Investments Measured at NAV [Member] | Bonds [Member]
CLO Collateral Assets	0.0	0.0
Investments Measured at NAV [Member] | Equity Securities [Member]
CLO Collateral Assets	0.0	0.0
Private Equity Fund Assets	0.0	0.0
Investments Measured at NAV [Member] | Debt Securities [Member]
Private Equity Fund Assets		0.0
Investments Measured at NAV [Member] | Private Equity Funds [Member]
Private Equity Fund Assets	$ 52.5	$ 368.2