Significant Transactions - Schedule of Assets Acquired and Liabilities Assumed, Bamboo (Details) - USD ($) $ in Millions	Dec. 31, 2025	Sep. 02, 2025	Dec. 31, 2024	Dec. 31, 2023
Other Significant Transactions [Line Items]
Goodwill	$ 614.1		$ 439.2	$ 168.8
Distinguished Transaction
Other Significant Transactions [Line Items]
Short-term investments, at fair value		$ 78.1
Restricted cash		0.4
Cash (restricted $0.4)		1.1
Premiums, commissions and fees receivable		34.6
Other assets		11.3
Debt		(100.6)
Premiums and commissions payable		(72.9)
Other liabilities		(52.2)
Net tangible assets acquired (liabilities assumed)		(100.6)
Goodwill		420.6
Other intangible assets		198.2
Deferred tax liabilities related to investment basis differences		(24.0)
Net assets acquired		$ 494.2