v3.26.1
RESERVE FOR CLAIMS AND CLAIM EXPENSES - Schedule of Prior Year Development of the Reserve for Net Claims and Claim Expenses (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses $ (199,425) $ (269,710) $ (361,440) $ (465,584)
Amortization of fair value adjustments     14,700 20,600
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)
Property        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (418,213) (453,634)
Property | Actuarial assumption changes        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (25,700)  
Property | Large catastrophe events        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (195,428) (174,839)
Property | 2025 Large Loss Events        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (26,424) 0
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     (78,291) (10,415)
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     (26,479) (52,710)
Property | 2022 Weather-Related Large Losses        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (37,433) (63,586)
Property | 2021 Weather-Related Large Losses        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (26,371) (27,372)
Property | 2020 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     3,096 (144)
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     (862) (1,074)
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     594 (4,874)
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     (3,258) (14,664)
Property | Total 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     (197,085) (245,695)
Amortization of fair value adjustments     3,700 5,200
Property | Total catastrophe and attritional net claims and claim expenses        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     (392,513) (420,534)
Casualty and Specialty        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses     56,773 (11,950)
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     95,825 19,839
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     (39,052) (31,789)
Amortization of fair value adjustments     11,100 15,400
Operating Segments | Property        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses (257,472) (266,576) (418,213) (453,634)
Operating Segments | Casualty and Specialty        
Liability for Catastrophe Claims [Line Items]        
Total net (favorable) adverse development of prior accident years net claims and claim expenses $ 58,047 $ (3,134) $ 56,773 $ (11,950)