The unexpired portion of premiums ceded on policies in force as of the balance sheet date.

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer.

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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.

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Third-Party Reinsurance - Reinsurance Recoverables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Ark Insurance Holdings Limited/Outrigger
Segment reporting information
Reinsurance recoverable on unpaid losses	$ 340.8	$ 505.0
Reinsurance recoverables on paid losses	27.4	31.1
Ceded unearned premiums	73.8	59.2
Reinsurance recoverables	442.0	595.3
Ceded	55.7	278.5	$ 128.1
Ark Insurance Holdings Limited/Outrigger \| Ark
Segment reporting information
Ceded	(15.6)
Ceded unearned premiums	(5.7)
Ark
Segment reporting information
Reinsurance recoverable on unpaid losses	340.8	505.0	$ 428.9	$ 433.4
Ark \| Ark
Segment reporting information
Ceded	$ (15.6)
Amount attributable to TPC Providers
Segment reporting information
Reinsurance recoverable on unpaid losses		$ 145.4