Third-Party Reinsurance - Remaining Gross and Net Reinsurance Recoverables (Details) - All Entities Except TCP Providers - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Reinsurance [Line Items]
Reinsurance recoverables		$ 372.0
Reinsurance Recoverables, Collateral		103.2
Net Reinsurance Recoverables		$ 268.8
Percent of reinsurance recoverables from insurers that are collateralized		100.00%
A+ or better
Reinsurance [Line Items]
Reinsurance recoverables	$ 173.8
Reinsurance Recoverables, Collateral	0.0
Net Reinsurance Recoverables	$ 173.8
Percent of reinsurance recoverables from insurers that are collateralized	64.70%
A- to A
Reinsurance [Line Items]
Reinsurance recoverables	$ 77.9
Reinsurance Recoverables, Collateral	0.0
Net Reinsurance Recoverables	$ 77.9
Percent of reinsurance recoverables from insurers that are collateralized	29.00%
B++ or lower and not rated
Reinsurance [Line Items]
Reinsurance recoverables	$ 120.3
Reinsurance Recoverables, Collateral	103.2
Net Reinsurance Recoverables	$ 17.1
Percent of reinsurance recoverables from insurers that are collateralized	6.30%