Restricted Securities Available For Sale (Restricted Securities Available For Sale) (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cost		$ 59.0	$ 46.4
Gross Unrealized Gains		0.1	0.0
Gross Unrealized Losses		0.5	0.3
Total restricted securities available for sale	[1]	58.6	46.1
US Government and agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		24.8	19.2
Gross Unrealized Gains		0.1	0.0
Gross Unrealized Losses		0.2	0.2
Total restricted securities available for sale		24.7	19.0
Corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		23.4	18.2
Gross Unrealized Gains		0.0	0.0
Gross Unrealized Losses		0.2	0.1
Total restricted securities available for sale		23.2	18.1
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		9.4	6.6
Gross Unrealized Gains		0.0	0.0
Gross Unrealized Losses		0.1	0.0
Total restricted securities available for sale		9.3	6.6
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		1.4	2.4
Gross Unrealized Gains		0.0	0.0
Gross Unrealized Losses		0.0	0.0
Total restricted securities available for sale		$ 1.4	$ 2.4

[1] Measured at fair value on a recurring basis.