Held for Sale - Financial Statement Disclosure (Details) - Discontinued Operations, Held-for-Sale - Bamboo Insurance Group - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Fixed maturity investments, at fair value	$ 37.7	$ 40.7
Short-term investments, at fair value	25.5	17.3
Total investments	63.2	58.0
Restricted cash	100.2	59.5
Cash (restricted $100.2 and $59.5)	136.5	74.5
Premiums, commissions and fees receivable	77.4	70.0
Goodwill and other intangible assets	343.0	355.0
Other assets	41.9	28.2
Total assets held for sale	662.0	585.7
Loss and loss adjustment expense reserves	28.5	17.8
Unearned insurance premiums	18.0	31.5
Premiums and commissions payable	114.8	88.1
Debt	104.6	0.0
Other liabilities	46.4	30.3
Total liabilities held for sale	312.3	167.7
Net assets held for sale	$ 349.7	$ 418.0