Investments (Breakdown Of Available-For-Sale Investments With Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Seed Money (64 Funds) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 0.2
Less than 12 Months, Gross Unrealized Losses	0
12 Months or Greater, Fair Value	11.5
12 Months or Greater, Gross Unrealized Losses	(0.5)
Total, Fair Value	11.7
Total, Gross Unrealized Losses	(0.5)
Seed Money (40 Funds) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	37.5
Less than 12 Months, Gross Unrealized Losses	(4.4)
12 Months or Greater, Fair Value	0
12 Months or Greater, Gross Unrealized Losses	0
Total, Fair Value	37.5
Total, Gross Unrealized Losses	$ (4.4)