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Reinsurance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Percentage of ceded earned premiums to gross earned premiums	43.00%	38.00%	40.00%	37.00%
Percentage of assumed earned premiums to net earned premiums	32.00%	29.00%	28.00%	26.00%
Program services and other fronting [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross losses and loss adjustment expenses	$ 593.9	$ 594.7	$ 1,200.0	$ 1,100.0

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- Definition

Percentage of ceded premiums earned by the entity to gross premiums earned.

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- References

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-Topic 944
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-Section S99
-Paragraph 2
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-Publisher FASB
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Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
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- Definition

Percentage of assumed premium earned to premium earned after effects of reinsurance, as disclosed in supplementary reinsurance information.

+ References

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