v3.26.1
Insurance Liabilities - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Jan. 20, 2017
Liability for Future Policy Benefit, Activity [Line Items]            
Contractual deductible recoverable amount $ 16,100   $ 16,100   $ 13,800  
Collateral held for deductible recoverable amounts 10,200   10,200   9,600  
Liability for unpaid losses and loss adjustment expenses, allowance for credit losses 14   14   14  
Unfavorable (favorable) prior year loss reserve development (246) $ 25 (372) $ (8)    
Net loss reserve discount $ 1,264   $ 1,264   $ 1,172  
Discount and spread, ceiling (as a percent) 4.50%   4.50%      
Discount and spread (as a percent) 4.50%   4.50%   4.50%  
Workers compensation tabular discount amount $ 157   $ 157   $ 141  
Workers compensation non tabular discount amount 1,100   1,100   $ 1,000  
Net loss reserve discount charge (28) (12) $ 20 (29)    
New York            
Liability for Future Policy Benefit, Activity [Line Items]            
Nontabular discount rate (as a percent)     5.00%      
NICO            
Liability for Future Policy Benefit, Activity [Line Items]            
Amortization of deferred gain on retroactive reinsurance $ (16) $ 93 $ 4 $ 110    
U.S. Run-Off Long Tail Insurance Lines | NICO | Accident Years 2015 and Prior            
Liability for Future Policy Benefit, Activity [Line Items]            
Risk Transferred - U.S. Commercial long-tail exposures for accident years 2015 and prior (as a percent)           80.00%
Ceded to NICO percent of paid losses (as a percent)           80.00%
Ceded to NICO net paid losses in excess           $ 25,000
Ceded to NICO net paid losses in excess, aggregate limit           25,000
NICO's limit of liability under the contract           20,000
Consideration paid, including interest           $ 10,200
Long-Duration Insurance            
Liability for Future Policy Benefit, Activity [Line Items]            
Ceded percentage 1   1   1  
Ceded reserves $ 763   $ 763   $ 797  
Other reserves $ 532   $ 532   $ 583