Restricted Securities Available For Sale (Schedule Of Cost And Estimated Fair Values Of Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Within one year, cost		$ 6.9	$ 4.0
Over one year to five years, cost		80.5	66.4
Over five years to ten years, cost		7.1	5.6
Over ten years, cost		0.1	0.1
Total restricted securities available for sale, cost		94.6	76.1
Within one year, estimated fair value		6.8	3.9
Over one year to five years, estimated fair value		79.1	63.0
Over five years to ten years, estimated fair value		7.2	5.3
Over ten years, fair value		0.1	0.1
Debt Securities, Available-for-sale, Restricted	[1]	$ 93.2	$ 72.3

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