Consolidated Investment Products (Fair Value Hierarchy Levels Of Investments Held And Notes Issued By Consolidated Investment Products) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Total assets at fair value	$ 1,752.2	$ 1,892.4
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Total assets at fair value	1,751.1	1,882.0
Significant Other Observable Inputs (Level 2) [Member]
Total assets at fair value	1.1	9.9
Significant Unobservable Inputs (Level 3) [Member]
Total assets at fair value	0	0.5
Consolidated Investment Products [Member] | Fair Value [Member]
Investments		289.9
CLO-related derivative assets	10.8	20.2
Total assets at fair value	6,639.8	7,226.2
Notes payable fair value	(5,512.9)	(5,865.4)
CLO-related derivative liabilities	(5.8)	(6.6)
Total liabilities at fair value	5,518.7	5,872.0
Consolidated Investment Products [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments		0
CLO-related derivative assets	0	0
Total assets at fair value	17.4	28.6
Notes payable fair value	0	0
CLO-related derivative liabilities	0	0
Total liabilities at fair value	0	0
Consolidated Investment Products [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments		0
CLO-related derivative assets	10.8	20.2
Total assets at fair value	5,693.3	6,224.8
Notes payable fair value	0	0
CLO-related derivative liabilities	(5.8)	(6.6)
Total liabilities at fair value	5.8	6.6
Consolidated Investment Products [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments		289.9
CLO-related derivative assets	0	0
Total assets at fair value	929.1	972.8
Notes payable fair value	(5,512.9)	(5,865.4)
CLO-related derivative liabilities	0	0
Total liabilities at fair value	5,512.9	5,865.4
Consolidated Investment Products [Member] | Bank Loans [Member] | Fair Value [Member]
Investments	5,354.3	5,910.6
Consolidated Investment Products [Member] | Bank Loans [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Bank Loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	5,354.3	5,910.6
Consolidated Investment Products [Member] | Bank Loans [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Bonds [Member] | Fair Value [Member]
Investments	292.8	261.1
Consolidated Investment Products [Member] | Bonds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	292.8	261.1
Consolidated Investment Products [Member] | Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Equity Securities [Member] | Fair Value [Member]
Investments	35.3	32.9
Consolidated Investment Products [Member] | Equity Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	35.3	32.9
Consolidated Investment Products [Member] | Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Private Equity Fund, Equity Securities [Member] | Fair Value [Member]
Investments	138.2	114.4
Consolidated Investment Products [Member] | Private Equity Fund, Equity Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	11.4	17.6
Consolidated Investment Products [Member] | Private Equity Fund, Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	0.1	0
Consolidated Investment Products [Member] | Private Equity Fund, Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	126.7	96.8
Consolidated Investment Products [Member] | Private Equity Fund, Debt securities [Member] | Fair Value [Member]
Investments	10.0
Consolidated Investment Products [Member] | Private Equity Fund, Debt securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	10.0
Consolidated Investment Products [Member] | Investments in Other Private Equity Funds [Member] | Fair Value [Member]
Investments	559.5	586.1
Consolidated Investment Products [Member] | Investments in Other Private Equity Funds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Investments in Other Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Investments in Other Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	559.5	586.1
Consolidated Investment Products [Member] | Debt Securities Issued By U.S. Treasury [Member] | Fair Value [Member]
Investments	6.0	11.0
Consolidated Investment Products [Member] | Debt Securities Issued By U.S. Treasury [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	6.0	11.0
Consolidated Investment Products [Member] | Debt Securities Issued By U.S. Treasury [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Debt Securities Issued By U.S. Treasury [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	0	0
Consolidated Investment Products [Member] | Real Estate Investment [Member] | Fair Value [Member]
Investments	232.9
Consolidated Investment Products [Member] | Real Estate Investment [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Investments	0
Consolidated Investment Products [Member] | Real Estate Investment [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investments	0
Consolidated Investment Products [Member] | Real Estate Investment [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investments	$ 232.9