Allowance for Credit Losses (Changes in Reinsurance Receivables Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Reinsurance Recoverables, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 5.4	$ 5.0
Current period change for credit losses	(0.6)	0.4
Ending balance	4.8	5.4
Corporate and Other
Reinsurance Recoverables, Allowance for Credit Losses [Roll Forward]
Beginning balance	0.7	0.5
Current period change for credit losses	(0.3)	0.2
Ending balance	0.4	0.7
Global Lifestyle | Operating Segments
Reinsurance Recoverables, Allowance for Credit Losses [Roll Forward]
Beginning balance	3.6	3.6
Current period change for credit losses	(0.3)	0.0
Ending balance	3.3	3.6
Global Housing | Operating Segments
Reinsurance Recoverables, Allowance for Credit Losses [Roll Forward]
Beginning balance	1.1	0.9
Current period change for credit losses	0.0	0.2
Ending balance	$ 1.1	$ 1.1