REINSURANCE - Schedule of Ratings from Rating Agencies and Unsecured Amounts Due from Reinsurers Exceeded 3% of Stockholders' Equity (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	$ 49,004	$ 245,760
Various Lloyd’s of London Syndicates
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	49,004	75,742
Florida Hurricane Catastrophe Fund “FHCF”
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	0	69,734
Markel Bermuda Ltd.
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	0	38,569
Everest Reinsurance Co
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	0	22,041
Renaissance Reinsurance Ltd.
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	0	20,875
DaVinci Reinsurance Ltd.
Ceded Credit Risk [Line Items]
Reinsurance unsecured amounts due from reinsurers	$ 0	$ 18,799
Customers with Greater than 3% of Equity \| Stockholders' Equity, Total \| Amounts Due From Reinsurers
Ceded Credit Risk [Line Items]
Unsecured amounts due from reinsurers exceeding a fixed percentage of stockholders equity	3.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

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