Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale By Aging Catagory) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months	$ 20.6	$ 23.4
Gross Unrealized Losses Less than 12 Months	(0.3)	(0.2)
Total Fair Value	20.6	23.4
Total Gross Unrealized Losses	(0.3)	(0.2)
US Government And Agency Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months	12.9	16.7
Gross Unrealized Losses Less than 12 Months	(0.2)	(0.1)
Total Fair Value	12.9	16.7
Total Gross Unrealized Losses	(0.2)	(0.1)
Commercial Paper [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months	4.6	2.8
Gross Unrealized Losses Less than 12 Months		(0.1)
Total Fair Value	4.6	2.8
Total Gross Unrealized Losses		(0.1)
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months	3.1	2.3
Gross Unrealized Losses Less than 12 Months	(0.1)
Total Fair Value	3.1	2.3
Total Gross Unrealized Losses	(0.1)
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months		1.5
Total Fair Value		1.5
Foreign Government Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Fair Value Less than 12 Months		0.1
Total Fair Value		$ 0.1