Consolidated Sponsored Investment Products (Fair Value Hierarchy Levels Of Investments Held By Consolidated Sponsored Investment Products) (Details) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Investments in Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	$ 58.0	$ 6.0
Unfunded commitments	0	0
Redemption notice period	10 days	10 days
Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	30.2	16.2
Unfunded commitments	35.0	35.6
Weighted average remaining term	7 years 7 months	8 years 1 month
Fair Value Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	288.5	93.2
Fair Value Measurements [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	200.3	43.2
Fair Value Measurements [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value		27.8
Fair Value Measurements [Member] | Investments in Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	58.0	6.0
Fair Value Measurements [Member] | Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	30.2	16.2
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	58.0	33.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value		27.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Investments in Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	58.0	6.0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	200.3	43.2
Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	200.3	43.2
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value		0
Significant Other Observable Inputs (Level 2) [Member] | Investments in Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Significant Other Observable Inputs (Level 2) [Member] | Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	30.2	16.2
Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value		0
Significant Unobservable Inputs (Level 3) [Member] | Investments in Fixed Income Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] | Investments in Other Private Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Consolidated sponsored investment products, fair value	$ 30.2	$ 16.2