Reinsurance (Schedule Of Trust Assets And Reinsurance Liabilities) (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reinsurance [Line Items]
Restricted cash and cash equivalents		$ 410.9	$ 380.2	$ 330.3
Debt Securities, Available-for-sale, Restricted	[1]	62.1	66.1
Accounts payable and accrued liabilities		175.0	186.7
Trust Assets [Member]
Reinsurance [Line Items]
Restricted cash and cash equivalents		0.3	0.7
Debt Securities, Available-for-sale, Restricted		62.1	66.1
Unearned Premium [Member]
Reinsurance [Line Items]
Accounts payable and accrued liabilities		44.6	48.5
Claims Reserve [Member]
Reinsurance [Line Items]
Accounts payable and accrued liabilities	[2]	$ 2.4	$ 2.3

[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.