Debt - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2026	Nov. 03, 2026	Jul. 31, 2026	Dec. 31, 2025
Debt Instrument
Extinguishment of Debt, Amount	$ 7.7
Stated Interest Rate of Debt	6.25%
Fortitude Re Experience Volatility Cover LOC Facility | Subsequent Event
Debt Instrument
Line of Credit Facility, Current Borrowing Capacity		$ 139.1
Line of Credit Facility, Maximum Borrowing Capacity		172.4
Letters of Credit Outstanding, Amount		$ 139.1
December 2023 standby LOC facility
Debt Instrument
Line of Credit Facility, Maximum Borrowing Capacity			$ 75.0
Line of Credit Facility, Expiration Date	Jul. 31, 2026
Amount Outstanding on Line of Credit			0.0
July 2021 standby LOC facility
Debt Instrument
Line of Credit Facility, Maximum Borrowing Capacity			75.0
Line of Credit Facility, Expiration Date	Jul. 31, 2026
Amount Outstanding on Line of Credit			$ 0.0
July 2026 standby LOC facility
Debt Instrument
Line of Credit Facility, Maximum Borrowing Capacity	$ 75.0
Amount Outstanding on Line of Credit	0.0
Letters of Credit Outstanding, Amount	75.0
April 2026 Senior LOC Facility
Debt Instrument
Line of Credit Facility, Maximum Borrowing Capacity	50.0
Amount Outstanding on Line of Credit	0.0			$ 0.0
Letters of Credit Outstanding, Amount	50.0
Revolving Credit Facility
Debt Instrument
Line of Credit Facility, Maximum Borrowing Capacity	500.0
Amount Outstanding on Line of Credit	0.0
Letters of Credit Outstanding, Amount	$ 1.3