Restricted Securities Available For Sale (Restricted Securities Available For Sale) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	$ 45.5	$ 48.5
Gross Unrealized Gains	0.1	0.0
Gross Unrealized Losses	0.3	0.2
Total restricted securities available for sale	45.3	48.3
US Government And Agency Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	20.4	21.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.1	0.1
Total restricted securities available for sale	20.3	21.7
Corporate bonds [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	16.9	17.1
Gross Unrealized Gains	0.1	0.0
Gross Unrealized Losses	0.2	0.1
Total restricted securities available for sale	16.8	17.0
Asset-backed Securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	5.0	5.5
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Total restricted securities available for sale	5.0	5.5
Mortgage-backed securities [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cost	3.2	4.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Total restricted securities available for sale	$ 3.2	$ 4.1