v3.25.4
RESERVE FOR CLAIMS AND CLAIM EXPENSES - Prior Year Development of the Reserve for Net Claims and Claim Expenses (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses $ (1,090,933) $ (851,334) $ (450,607)
Actuarial assumption changes      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses   9,962  
Property      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (1,089,196) (818,852) (408,905)
Property | Actuarial assumption changes      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (33,100)   840
Property | Large and small catastrophe events and attritional loss movements      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (1,056,096) (828,814) (409,745)
Property | Large catastrophe events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (580,955) (622,198) (309,820)
Property | 2024 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (131,056) 0 0
Property | 2023 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (84,617) (31,899) 0
Property | 2022 Weather-Related Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (258,848) (284,327) (85,653)
Property | 2021 Weather-Related Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (32,502) (180,028) (36,949)
Property | 2020 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (15,294) (47,512) (42,577)
Property | 2019 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (5,130) (14,445) (43,850)
Property | 2018 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (19,424) (38,295) (40,050)
Property | 2017 Large Loss Events      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (34,084) (25,692) (46,404)
Property | Other      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses 0 0 (14,337)
Property | Small catastrophe events and attritional loss movements      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (475,141) (206,616) (99,925)
Amortization of fair value adjustments 10,300 15,200 4,000
Property | Operating Segments      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (1,089,196) (818,852) (408,905)
Casualty and Specialty      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (1,737) (32,482) (41,702)
Casualty and Specialty | Actuarial methods - actual reported claims less than expected claims      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses (21,576) (67,595) (44,612)
Amortization of fair value adjustments 30,800 44,700 15,600
Casualty and Specialty | Actuarial assumption changes      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses 19,839 35,113 2,910
Casualty and Specialty | Operating Segments      
Liability for Catastrophe Claims [Line Items]      
Total net (favorable) adverse development of prior accident years net claims and claim expenses $ (1,737) $ (32,482) $ (41,702)