Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	$ 52.5	$ 53.9
Gross Unrealized Losses	(0.2)	(0.3)
Total restricted securities available for sale, estimated fair value	52.3	53.6
Commercial Paper [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	24.1	23.9
Total restricted securities available for sale, estimated fair value	24.1	23.9
US Government And Agency Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	19.9	22.3
Gross Unrealized Losses	(0.1)	(0.2)
Total restricted securities available for sale, estimated fair value	19.8	22.1
Certificates Of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	5.1	4.6
Total restricted securities available for sale, estimated fair value	5.1	4.6
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	3.4	3.1
Gross Unrealized Losses	(0.1)	(0.1)
Total restricted securities available for sale, estimated fair value	$ 3.3	$ 3.0