v3.26.1
Reserve for Unpaid Losses and Loss Adjustment Expenses - P&C Liabilities for Unpaid Losses and Loss Adjustment Expense (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]            
Beginning liabilities for unpaid losses and loss adjustment expenses, gross $ 46,268   $ 46,268      
Less: payments            
Ending liabilities for unpaid losses and loss adjustment expenses, gross     47,146      
Reinsurance Contract [Axis]: Adverse Development Cover A&E            
Provision for unpaid losses and loss adjustment expense            
Increase (Decrease) in Deferred Revenue 36          
Less: payments            
Amortization of Deferred Gain on Retroactive Reinsurance     36      
Reinsurance Contract [Axis]: Adverse Development Cover Navigators Group            
Provision for unpaid losses and loss adjustment expense            
Increase (Decrease) in Deferred Revenue   $ (24)   $ (56)    
Less: payments            
Amortization of Deferred Gain on Retroactive Reinsurance       (56)    
Property, Liability and Casualty Insurance Product Line            
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]            
Beginning liabilities for unpaid losses and loss adjustment expenses, gross $ 38,155   38,155 36,404    
Reinsurance and other recoverables   6,631 6,523 6,631 $ 6,723 $ 6,753
Liability for Unpaid Claims and Claims Adjustment Expense, Net   30,727 32,458 30,727 31,432 29,651
Provision for unpaid losses and loss adjustment expense            
Current accident year     5,699 5,670    
Prior accident year development [1]     (152) (309)    
Total provision for unpaid losses and loss adjustment expenses     5,547 5,361    
Less: payments            
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year     (1,065) (1,175)    
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years     (3,486) (3,205)    
Total payments     (4,551) (4,380)    
Foreign currency adjustment     (6) 39    
Ending liabilities for unpaid losses and loss adjustment expenses, net   30,727 32,458 30,727    
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments   (6,631) (6,523) (6,631) $ (6,723) $ (6,753)
Ending liabilities for unpaid losses and loss adjustment expenses, gross   $ 37,358 38,981 37,358    
Property, Liability and Casualty Insurance Product Line | Reinsurance Contract [Axis]: Adverse Development Cover A&E            
Provision for unpaid losses and loss adjustment expense            
Increase (Decrease) in Deferred Revenue     $ (36)      
Property, Liability and Casualty Insurance Product Line | Reinsurance Contract [Axis]: Adverse Development Cover Navigators Group            
Provision for unpaid losses and loss adjustment expense            
Increase (Decrease) in Deferred Revenue       $ (56)