Consolidated Investment Products (Fair Value Hierarchy Levels Of Investments Held And Notes Issued By Consolidated Investment Products) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Investments Of Consolidated Investment Products	$ 5,762,800,000	$ 4,734,700,000
CLO notes	(11,177,200,000)	(10,293,200,000)
Fair Value [Member]
Investments Of Consolidated Investment Products	5,762,800,000	4,734,700,000
Total liabilities at fair value	(5,149,600,000)	(4,181,700,000)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Investments Of Consolidated Investment Products	9,700,000	50,800,000
Total liabilities at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member]
Investments Of Consolidated Investment Products	4,979,200,000	4,183,000,000
Total liabilities at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member]
Investments Of Consolidated Investment Products	773,900,000	500,900,000
Total liabilities at fair value	(5,149,600,000)	(4,181,700,000)
Bank Loans [Member] | Fair Value [Member]
CLO Collateral Assets	4,883,900,000	4,035,800,000
Bank Loans [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
CLO Collateral Assets	0	0
Bank Loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	4,883,900,000	4,035,800,000
Bank Loans [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0	0
Bonds [Member] | Fair Value [Member]
CLO Collateral Assets	88,900,000	133,100,000
Bonds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
CLO Collateral Assets	0	0
Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	88,900,000	133,100,000
Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0	0
Equity Securities [Member] | Fair Value [Member]
CLO Collateral Assets	6,400,000	14,100,000
Private Equity Fund Assets	337,900,000	106,000,000
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
CLO Collateral Assets	0	0
Private Equity Fund Assets	9,700,000	47,300,000
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO Collateral Assets	6,400,000	14,100,000
Private Equity Fund Assets	0	0
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO Collateral Assets	0	0
Private Equity Fund Assets	328,200,000	58,700,000
Debt Securities [Member] | Fair Value [Member]
Private Equity Fund Assets	35,700,000
Debt Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Private Equity Fund Assets	0
Debt Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Private Equity Fund Assets	0
Debt Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Private Equity Fund Assets	35,700,000
Private Equity Funds [Member] | Fair Value [Member]
Private Equity Fund Assets	410,000,000	442,200,000
Private Equity Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Private Equity Fund Assets	0	0
Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Private Equity Fund Assets	0	0
US Treasury Notes Securities [Member] | Fair Value [Member]
Private Equity Fund Assets		3,500,000
US Treasury Notes Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Private Equity Fund Assets		3,500,000
US Treasury Notes Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Private Equity Fund Assets		0
US Treasury Notes Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Private Equity Fund Assets		0
Asset-backed Securities [Member] | Fair Value [Member]
CLO notes	(5,149,600,000)	(4,181,700,000)
Asset-backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
CLO notes	0	0
Asset-backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
CLO notes	0	0
Asset-backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
CLO notes	$ (5,149,600,000)	$ (4,181,700,000)