Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 52.2	$ 46.3
Gross Unrealized Losses	(0.3)	(0.2)
Total restricted securities available for sale, estimated fair value	51.9	46.1
US Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	25.5	20.6
Gross Unrealized Losses	(0.2)	(0.1)
Total restricted securities available for sale, estimated fair value	25.3	20.5
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	19.7	18.9
Gross Unrealized Losses		(0.1)
Total restricted securities available for sale, estimated fair value	19.7	18.8
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	3.0	3.3
Gross Unrealized Losses	(0.1)
Total restricted securities available for sale, estimated fair value	2.9	3.3
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	4.0	3.3
Total restricted securities available for sale, estimated fair value	4.0	3.3
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost		0.2
Total restricted securities available for sale, estimated fair value		$ 0.2