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Third-Party Reinsurance - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Reinsurance [Line Items]
Reinsurance recoverables on unpaid losses		$ 375.5		$ 425.3
Reinsurance recoverables on paid losses		23.2		6.0
Loss and loss adjustment expense reserves	$ 428.9	375.5	$ 396.0	425.3	$ 447.5	$ 433.4
TPC Providers
Reinsurance [Line Items]
Reinsurance recoverables				314.6
Loss and loss adjustment expense reserves	276.8		$ 207.3	314.6	$ 331.0	$ 319.2
Ark
Reinsurance [Line Items]
Reinsurance recoverables	$ 448.4	398.7		$ 431.3
Ark \| TPC Providers
Reinsurance [Line Items]
Reinsurance recoverables		182.4
Ark \| Third Point Re
Reinsurance [Line Items]
Annual crediting rate	3.00%
Decrease in investment	$ 31.7
Carrying value of investment		$ 20.1