Third-Party Reinsurance - Reinsurance Recoverables (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Ark
Reinsurance [Line Items]
Reinsurance recoverables on unpaid losses	$ 362.7	$ 505.0
Reinsurance recoverables on paid losses	23.3	31.1
Ceded unearned premiums	283.7	59.2
Reinsurance recoverables	$ 669.7	595.3
Ark \| Third Point Re
Reinsurance [Line Items]
Annual crediting rate	3.00%
Carrying value of investment	$ 20.1	20.4
P&C Insurance and Reinsurance (Ark/WM Outrigger)
Reinsurance [Line Items]
Reinsurance recoverables on unpaid losses	0.6
Ceded unearned premiums	$ 87.6
TPC Providers
Reinsurance [Line Items]
Reinsurance recoverables on unpaid losses		$ 145.4

Fair value of investment in security owned.

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Rate of interest credited to policyholder deposits.

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Amount before valuation allowance recoverable 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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