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Segment Information - Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment reporting information
Earned insurance premiums	$ 1,777.1	$ 1,691.6	$ 1,440.9
Commission and fee revenues	284.5	149.4	13.2
Other revenues	198.7	55.8	69.0
Total	2,260.3	1,896.8	1,523.1
United States
Segment reporting information
Earned insurance premiums	26.7	2.8	5.2
Commission and fee revenues	268.1	134.6	0.0
Other revenues	198.7	55.8	69.0
Total	493.5	193.2	74.2
United Kingdom
Segment reporting information
Earned insurance premiums	1,045.3	956.8	791.7
Commission and fee revenues	0.0	0.0	0.0
Other revenues	0.0	0.0	0.0
Total	1,045.3	956.8	791.7
Bermuda
Segment reporting information
Earned insurance premiums	705.1	732.0	644.0
Commission and fee revenues	0.0	0.0	0.0
Other revenues	0.0	0.0	0.0
Total	705.1	732.0	644.0
Other
Segment reporting information
Earned insurance premiums	0.0	0.0	0.0
Commission and fee revenues	16.4	14.8	13.2
Other revenues	0.0	0.0	0.0
Total	$ 16.4	$ 14.8	$ 13.2

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- Definition

Income from agency and brokerage operations (includes sales of annuities and supplemental contracts); service charges, commissions, and fees from the sale of insurance and related services; and management fees from separate accounts, deferred annuities, and universal life products.

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