Consolidated Sponsored Investment Products (Fair Value Hierarchy Levels Of Investments Held By Consolidated Sponsored Investment Products) (Details) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	$ 290.3
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.7
Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	204.2
Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	204.2
Fixed Income Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Fixed Income Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	204.2
Fixed Income Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.7
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.7
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	35.0
Fixed Income Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Fixed Income Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Fixed Income Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	50.4
Investments in Other Private Equity Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments in Other Private Equity Funds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments in Other Private Equity Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments Measured at NAV [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	85.4
Investments Measured at NAV [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments Measured at NAV [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	0.0
Investments Measured at NAV [Member] | Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	35.0
Investments Measured at NAV [Member] | Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Consolidated Sponsored Investment Products, Fair Value Disclosure	$ 50.4