Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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	$ 570.6		$ 595.3
P&C Insurance and Reinsurance (Ark/WM Outrigger)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross beginning balance	1,296.5	$ 894.7
Less: beginning reinsurance recoverable on unpaid losses	(505.0)	(428.9)
Net loss and LAE reserves	791.5	465.8
Loss and LAE incurred relating to:
Current year losses	139.2	125.7
Prior year losses	8.6	(3.7)
Net incurred losses and LAE	147.8	122.0
Loss and LAE paid relating to:
Current year losses	(4.0)	(0.6)
Prior year losses	(87.7)	(39.4)
Net paid loss and LAE	(91.7)	(40.0)
Change in TPC providers’ participation	145.4	57.5
Foreign currency translation and other adjustments to loss and LAE reserves	3.7	(1.7)
Net ending balance	996.7	603.6
Plus: ending reinsurance recoverable on unpaid losses	348.9	396.0
Gross ending balance	1,345.6	999.6
Reinsurance recoverables	570.6		$ 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	(145.4)	(276.8)
Loss and LAE paid relating to:
Reinsurance recoverables		$ 207.3
P&C Insurance and Reinsurance (Ark/WM Outrigger) | TPC Providers | Ark
Loss and LAE paid relating to:
Reinsurance recoverables	$ 0.0