Reinsurance (Schedule Of Trust Assets And Reinsurance Liabilities) (Details) - USD ($) $ in Millions		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reinsurance [Line Items]
Restricted cash and cash equivalents		$ 410.0	$ 410.9	$ 380.2
Debt Securities, Available-for-sale, Restricted	[1]	72.3	62.1
Accounts payable and accrued liabilities		260.8	175.0
Trust Assets [Member]
Reinsurance [Line Items]
Restricted cash and cash equivalents		0.4	0.3
Debt Securities, Available-for-sale, Restricted		72.3	62.1
Unearned Premium [Member]
Reinsurance [Line Items]
Accounts payable and accrued liabilities		54.4	44.6
Claims Reserve [Member]
Reinsurance [Line Items]
Accounts payable and accrued liabilities	[2]	$ 3.1	$ 2.4

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

[2] The claims reserve represents our liability for incurred-but-not-reported claims and is estimated based on historical claims experience.