Reinsurance and Catastrophes - Total Amounts of Reinsurance Recoverables On Unpaid Insurance Reserves (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Summary of reinsurance recoverable on unpaid insurance reserves
Reinsurance balances receivable	$ 462.5	$ 119.6
Reinsurance companies
Summary of reinsurance recoverable on unpaid insurance reserves
Reinsurance balances receivable	3.1	10.4
State insurance facilities
Summary of reinsurance recoverable on unpaid insurance reserves
Reinsurance balances receivable	97.7	99.9
Group benefits
Summary of reinsurance recoverable on unpaid insurance reserves
Reinsurance balances receivable	352.4	0.0
Life and health
Summary of reinsurance recoverable on unpaid insurance reserves
Reinsurance balances receivable	$ 9.3	$ 9.3

Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(6))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=99404803&loc=d3e21409-158489

Name:	us-gaap_ReinsuranceRecoverables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant