Insurance Liabilities - Liability for Unpaid Claims (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Change in unpaid claims
Balance at beginning of period, unpaid claims	$ 2,659.4	$ 2,534.9
Balance at beginning of period, reinsurance recoverables for unpaid claims	442.1	436.9
Net balance at beginning of period, unpaid claims	2,217.3	2,098.0
Incurred:
Incurred: Current year	1,232.2	736.0
Incurred: Prior years	37.1	441.7
Total incurred	1,269.3	1,177.7
Payments:
Payments: Current year	791.1	313.6
Payments: Prior years	384.6	773.2
Total payments	1,175.7	1,086.8
Net balance at end of period, unpaid claims	2,310.9	2,188.9
Balance at end of period, reinsurance recoverables for unpaid claims	477.5	437.9
Balance at end of period, unpaid claims	2,788.4	2,626.8
Amount not included in the rollforward above:
Claim adjustment expense liabilities	$ 60.2	$ 59.5