Investments (Breakdown Of Available-For-Sale Investments With Unrealized Losses) (Details) (Seed Money Funds [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Seed Money Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 123.9	$ 69.0
Less than 12 Months, Gross Unrealized Losses	(3.5)	(0.8)
12 Months or Greater, Fair Value	3.6	0.2
12 Months or Greater, Gross Unrealized Losses	(0.8)	(0.1)
Total, Fair Value	127.5	69.2
Total, Gross Unrealized Losses	$ (4.3)	$ (0.9)