v3.26.1
Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]    
Claims and claim adjustment expense reserves at beginning of year $ 65,737  
Claims and claim adjustment expense reserves at end of period 66,912  
Property-casualty [Member]    
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]    
Claims and claim adjustment expense reserves at beginning of year   $ 64,088
Reinsurance recoverables on unpaid losses   7,669
Net reserves at beginning of year   56,419
Estimated claims and claim adjustment expenses for claims arising in the current year 6,739 8,338
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (385) (360)
Total increases 6,354 7,978
Claims and claim adjustment expense payments for claims arising in current year 1,174 1,856
Claims and claim adjustment expense payments for claims arising in prior years 4,146 4,415
Total payments 5,320 6,271
Net reserves disposed of related to the divestiture of the Canadian business (1,627)  
Unrealized foreign exchange (gain) loss (32) 59
Net reserves at end of period 59,221 58,185
Reinsurance recoverables on unpaid losses 7,687 7,787
Claims and claim adjustment expense reserves at end of period 66,908 $ 65,972
Amount of increase in gross claims and claim adjustment expense reserves 1,180  
Accident and health [Member]    
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]    
Claims and claim adjustment expense reserves at beginning of year 3  
Claims and claim adjustment expense reserves at end of period 4  
Before Reclassifications of Held For Sale [Member] | Property-casualty [Member]    
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]    
Claims and claim adjustment expense reserves at beginning of year 67,643  
Reinsurance recoverables on unpaid losses 7,797  
Net reserves at beginning of year 59,846  
Held for Sale Reclassification [Member]    
Reconciliation of beginning and ending reserve balances for claims and claim adjustment expenses [Roll Forward]    
Claims and claim adjustment expense reserves at beginning of year $ (1,909)