Description of Business and Summary of Significant Accounting Policies - Deferred Policy Acquisition Costs, net of Ceding Commissions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amortized deferred policy acquisition costs	$ 32.3	$ 17.8

Amount of amortization expense (reversal of expense) for deferred policy acquisition costs.

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Name:	us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration