Statutory Requirements and Dividend Restrictions - Statutory Requirements (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Bermuda
Effects of Reinsurance [Line Items]
Required statutory capital and surplus	$ 735.0	$ 622.2
Actual statutory capital and surplus	1,920.0	1,503.5
United Kingdom
Effects of Reinsurance [Line Items]
Required statutory capital and surplus	505.0	552.1
Actual statutory capital and surplus	955.0	848.0
Republic of Ireland
Effects of Reinsurance [Line Items]
Required statutory capital and surplus	95.0	84.3
Actual statutory capital and surplus	$ 180.0	$ 138.6

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- Definition

The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country.

+ References

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//1943274/2147479440/944-210-S99-1

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-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479989/944-505-50-1

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- Definition

Amount of statutory capital required to be maintained as of the balance sheet date under prescribed or permitted statutory accounting practices.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 944
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479989/944-505-50-1

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