Historical Loss and LAE Development - Reserve Development (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
(Favorable)/Unfavorable Reserve Development
Prior accident years	$ (95,309)	$ (108,547)	$ (122,579)
Casualty Segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	(52,878)	(78,498)	(87,225)
Property segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	(33,143)	(21,196)	(24,927)
Surety Segment
(Favorable)/Unfavorable Reserve Development
Prior accident years	$ (9,288)	$ (8,853)	$ (10,427)

Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-3

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration