Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	$ 47.8	$ 46.3
Gross Unrealized Losses	(0.3)	(0.2)
Total restricted securities available for sale	47.5	46.1
US Government And Agency Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	25.3	20.6
Gross Unrealized Losses	(0.2)	(0.1)
Total restricted securities available for sale	25.1	20.5
Commercial Paper [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	15.4	18.9
Gross Unrealized Losses		(0.1)
Total restricted securities available for sale	15.4	18.8
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	3.3	3.3
Gross Unrealized Losses	(0.1)
Total restricted securities available for sale	3.2	3.3
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	3.8	3.3
Total restricted securities available for sale	3.8	3.3
Foreign Government Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost		0.2
Total restricted securities available for sale		$ 0.2