Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale By Aging Category) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	$ 15.0	$ 26.0
Gross Unrealized Losses Less than 12 Months	(0.1)	(0.3)
Estimated Fair Value 12 Months or More	2.0
Gross Unrealized Losses 12 Months or More	(0.1)
Total Estimated Fair Value	17.0	26.0
Total Gross Unrealized Losses	(0.2)	(0.3)
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	6.9	10.0
Total Estimated Fair Value	6.9	10.0
US Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	5.8	11.8
Gross Unrealized Losses Less than 12 Months	(0.1)	(0.2)
Estimated Fair Value 12 Months or More	1.1
Total Estimated Fair Value	6.9	11.8
Total Gross Unrealized Losses	(0.1)	(0.2)
Certificates Of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	1.0	1.9
Total Estimated Fair Value	1.0	1.9
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	1.3	2.3
Gross Unrealized Losses Less than 12 Months		(0.1)
Estimated Fair Value 12 Months or More	0.9
Gross Unrealized Losses 12 Months or More	(0.1)
Total Estimated Fair Value	2.2	2.3
Total Gross Unrealized Losses	$ (0.1)	$ (0.1)