Investments (Breakdown Of Available-For-Sale Investments With Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013 fund	Dec. 31, 2012 fund
Number of affiliated funds holding seed money	41	52
Seed Money Funds [Member]
Less Than 12 Months, Fair Value	$ 11.6	$ 0.2
Less than 12 Months, Gross Unrealized Losses	(0.2)	0
12 Months or Greater, Fair Value	0.2	11.5
12 Months or Greater, Gross Unrealized Losses	(0.1)	(0.5)
Total, Fair Value	11.8	11.7
Total, Gross Unrealized Losses	$ (0.3)	$ (0.5)