Schedule V - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Premiums receivable from underwriting activities
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 25.0	$ 30.2	$ 34.0
Charged to Costs and Expenses	(4.0)	(5.2)	(3.8)
Charged to Other Accounts	0.0	0.0	0.0
Deductions	0.0	0.0	0.0
Balance at End of Year	21.0	25.0	30.2
Reinsurance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	0.0	0.0	0.0
Charged to Costs and Expenses	0.0	0.0	0.0
Charged to Other Accounts	0.0	0.0	0.0
Deductions	0.0	0.0	0.0
Balance at End of Year	$ 0.0	$ 0.0	$ 0.0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column B))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09(Column E))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-4

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Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

+ References

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Amount of increase in valuation and qualifying accounts and reserves from charge to accounts other than cost and expense.

+ References

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Amount of decrease in valuation and qualifying accounts and reserves.

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