Restricted Securities Available For Sale (Schedule Of Cost And Estimated Fair Values Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Within one year, cost		$ 2.9	$ 1.1
Over one year to five years, cost		56.9	58.1
Over five years to ten years, cost		2.1	4.7
Over ten years, cost		0.1	0.2
Total restricted securities available for sale, cost		62.0	64.1
Within one year, estimated fair value		3.0	1.1
Over one year to five years, estimated fair value		57.0	60.0
Over five years to ten years, estimated fair value		2.0	4.8
Over ten years, fair value		0.1	0.2
Debt Securities, Available-for-sale, Restricted	[1]	$ 62.1	$ 66.1

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