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Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
TPC Providers | Ark
Loss and LAE paid relating to:
Percent of underwriting capital provided by third parties						0.00%	42.80%	58.30%
Ark
Loss and LAE paid relating to:
Reinsurance recoverables	$ 669.7		$ 669.7		$ 595.3
P&C Insurance and Reinsurance (Ark/WM Outrigger)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance	1,345.6	$ 999.6	1,296.5	$ 894.7
Less: beginning reinsurance recoverable on unpaid losses	(348.9)	(396.0)	(505.0)	(428.9)
Net loss and LAE reserves	996.7	603.6	791.5	465.8
Loss and LAE incurred relating to:
Current year losses	156.5	143.2	295.7	268.9
Prior year losses	11.0	(22.7)	19.6	(26.4)
Net incurred losses and LAE	167.5	120.5	315.3	242.5
Loss and LAE paid relating to:
Current year losses	(5.6)	(14.1)	(9.6)	(14.7)
Prior year losses	(103.0)	(54.4)	(190.7)	(93.8)
Net paid loss and LAE	(108.6)	(68.5)	(200.3)	(108.5)
Change in TPC providers’ participation	0.0	0.0	145.4	57.5
Foreign currency translation and other adjustments to loss and LAE reserves	2.7	(9.0)	6.4	(10.7)
Net ending balance	1,058.3	646.6	1,058.3	646.6
Plus: ending reinsurance recoverable on unpaid losses	362.7	375.5	362.7	375.5
Gross ending balance	1,421.0	1,022.1	1,421.0	1,022.1
Reinsurance recoverables	669.7		669.7		$ 595.3
P&C Insurance and Reinsurance (Ark/WM Outrigger) | TPC Providers
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less: beginning reinsurance recoverable on unpaid losses	(0.0)	(207.3)	(145.4)	(276.8)
Loss and LAE paid relating to:
Reinsurance recoverables	$ 0.0	$ 182.4	$ 0.0	$ 182.4

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- Definition

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs.

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Amount of foreign currency gain (loss) which decreases (increases) the cost of settling unpaid claims after deduction of reinsurance recoveries. Includes, but is not limited to, claims which have been incurred but not reported.

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

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Sum of adjustments to the estimated reserve for unpaid claims and claims adjustment expense.

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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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