Statutory Requirements and Dividend Restrictions - Statutory Net Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Bermuda
Effects of Reinsurance [Line Items]
Statutory net income (loss)	$ 158.3	$ 67.3	$ 345.2
United Kingdom
Effects of Reinsurance [Line Items]
Statutory net income (loss)	162.9	115.0	68.1
Republic of Ireland
Effects of Reinsurance [Line Items]
Statutory net income (loss)	$ (8.4)	$ (3.8)	$ 19.3

Amount of net income for the period determined using accounting principles prescribed or permitted by insurance regulators.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

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Balance Type:	credit
Period Type:	duration