v3.26.1
RESERVE FOR LOSSES AND LAE - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Oct. 01, 2025
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year       $ 4,421 $ 5,307  
Prior year losses       (33)    
Funds held under reinsurance treaties   $ 267   267   $ 267
Funds held by reinsureds   1,408   1,408   1,326
Incurred losses and LAE   2,170 $ 2,472 4,388 5,366  
Reinsurance recoverables, adverse development reinsurance agreement           1,250
Reinsurance Contract [Axis]: Adverse Development Cover Reinsurance Agreements            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Funds held under reinsurance treaties   5,400   5,400    
Deferred gain on sale current       8   3
Reinsurance recoverables, adverse development reinsurance agreement   $ 1,260   1,260    
Policyholder benefits and claims incurred, ceded       1,260   1,250
Reinsurance Contract [Axis]: Adverse Development Cover Reinsurance Agreements | State National Reinsurer            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Payments for reinsurance $ 1,300          
Co-participation per layer $ 1,300          
Reinsurance, excess retention (in percent) 85.70%          
Funds held under reinsurance agreement, excess of liability $ 600          
Funds held by reinsureds $ 250          
Reinsurance, excess retention unexpired limit, amount reinsured, per policy       592   597
Reinsurance Contract [Axis]: Adverse Development Cover Reinsurance Agreements | MS Transverse Reinsurance            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Payments for reinsurance       $ 122    
Reinsurance, excess retention (in percent)       80.00%    
Funds held under reinsurance agreement, excess of liability       $ 400    
Incurred losses and LAE       122    
Reinsurance, excess retention unexpired limit, amount reinsured, per policy       400   $ 400
Higher Premiums Earned            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Decrease in earned premium growth       (556)    
Catastrophe Losses            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year       224    
Decrease in earned premium growth       (330)    
Prior year losses       (44)    
Washington D.C. Aviation Incident            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year         $ 83  
Attritional Losses            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Prior year losses       11    
Well-Seasoned Attritional Property Reserves            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Prior year losses       (99)    
Baltimore Bridge collapse            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Prior year losses       55    
Hurricane, Typhoons, Cyclones, Other Weather Related events            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year       129    
Foreign Conflict            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year       85    
Earthquake            
Reserve For Losses LAE And Future Policy Benefit Reserve [Line Items]            
Current year       $ 10