Restricted Securities Available For Sale (Restricted Securities Available For Sale) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost		$ 58.3	$ 59.0
Gross Unrealized Gains		1.0	0.1
Gross Unrealized Losses		0.0	0.5
Total restricted securities available for sale	[1]	59.3	58.6
Corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		25.3	23.4
Gross Unrealized Gains		0.5	0.0
Gross Unrealized Losses		0.0	0.2
Total restricted securities available for sale		25.8	23.2
US Government and agency securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		21.3	24.8
Gross Unrealized Gains		0.4	0.1
Gross Unrealized Losses		0.0	0.2
Total restricted securities available for sale		21.7	24.7
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		11.2	9.4
Gross Unrealized Gains		0.1	0.0
Gross Unrealized Losses		0.0	0.1
Total restricted securities available for sale		11.3	9.3
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		0.5	1.4
Gross Unrealized Gains		0.0	0.0
Gross Unrealized Losses		0.0	0.0
Total restricted securities available for sale		$ 0.5	$ 1.4

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