Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale By Aging Category) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	$ 28.3	$ 26.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(0.1)	(0.3)
Estimated Fair Value 12 Months or More	5.2	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(0.1)	0
Total Estimated Fair Value	33.5	26.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(0.2)	(0.3)
Corporate Bond [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	15.3	2.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	(0.1)	(0.1)
Estimated Fair Value 12 Months or More	2.7	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0	0
Total Estimated Fair Value	18.0	2.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(0.1)	(0.1)
US Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	9.3	11.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0	(0.2)
Estimated Fair Value 12 Months or More	2.5	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	(0.1)	0
Total Estimated Fair Value	11.8	11.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	(0.1)	(0.2)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months	3.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss	0
Estimated Fair Value 12 Months or More	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss	0
Total Estimated Fair Value	3.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss	0
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months		10.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		0
Estimated Fair Value 12 Months or More		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		0
Total Estimated Fair Value		10.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		0
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value Less than 12 Months		1.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss		0
Estimated Fair Value 12 Months or More		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss		0
Total Estimated Fair Value		1.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss		$ 0