Restricted Securities Available For Sale (Restricted Securities Available For Sale) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	$ 53.9	$ 46.3
Gross Unrealized Gains
Gross Unrealized Losses	(0.3)	(0.2)
Total restricted securities available for sale	53.6	46.1
Commercial Paper [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	23.9	18.9
Gross Unrealized Gains
Gross Unrealized Losses		(0.1)
Total restricted securities available for sale	23.9	18.8
US Government And Agency Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	22.3	20.6
Gross Unrealized Gains
Gross Unrealized Losses	(0.2)	(0.1)
Total restricted securities available for sale	22.1	20.5
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	4.6	3.3
Gross Unrealized Gains
Total restricted securities available for sale	4.6	3.3
Corporate Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	3.1	3.3
Gross Unrealized Gains
Gross Unrealized Losses	(0.1)
Total restricted securities available for sale	3.0	3.3
Foreign Government Bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost		0.2
Gross Unrealized Gains
Total restricted securities available for sale		$ 0.2