Restricted Securities Available For Sale (Schedule Of Restricted Securities Available For Sale By Aging Category) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	$ 33.4	$ 37.1
Gross Unrealized Losses, Less than 12 Months	(0.3)	(0.2)
Estimated Fair Value,12 Months or More	0.0	2.4
Gross Unrealized Losses, 12 Months or More	0.0	0.0
Total Estimated Fair Value	33.4	39.5
Total Gross Unrealized Losses	(0.3)	(0.2)
US Government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	16.4	16.0
Gross Unrealized Losses, Less than 12 Months	(0.1)	(0.1)
Estimated Fair Value,12 Months or More	0.0	0.7
Gross Unrealized Losses, 12 Months or More	0.0	0.0
Total Estimated Fair Value	16.4	16.7
Total Gross Unrealized Losses	(0.1)	(0.1)
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	11.8	12.6
Gross Unrealized Losses, Less than 12 Months	(0.2)	(0.1)
Estimated Fair Value,12 Months or More	0.0	1.7
Gross Unrealized Losses, 12 Months or More	0.0	0.0
Total Estimated Fair Value	11.8	14.3
Total Gross Unrealized Losses	(0.2)	(0.1)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	2.8	5.4
Gross Unrealized Losses, Less than 12 Months	0.0	0.0
Estimated Fair Value,12 Months or More	0.0	0.0
Gross Unrealized Losses, 12 Months or More	0.0	0.0
Total Estimated Fair Value	2.8	5.4
Total Gross Unrealized Losses	0.0	0.0
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value, Less than 12 Months	2.4	3.1
Gross Unrealized Losses, Less than 12 Months	0.0	0.0
Estimated Fair Value,12 Months or More	0.0	0.0
Gross Unrealized Losses, 12 Months or More	0.0	0.0
Total Estimated Fair Value	2.4	3.1
Total Gross Unrealized Losses	$ 0.0	$ 0.0