v3.26.3
Insurance Claim Reserves (Details) - Reserve Detail for Claims and Claim Adjustment Expenses - USD ($)
$ in Millions
 9 Months Ended
Sep. 30, 2026
Sep. 30, 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 68,130  
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 19,861 21,959
Estimated decrease in claims and claim adjustment expenses for claims arising in prior years (1,148) (648)
Total increases 18,713 21,311
Claims and claim adjustment expense payments for claims arising in current year 6,254 7,597
Claims and claim adjustment expense payments for claims arising in prior years 10,299 10,623
Total payments 16,553 18,220
Net reserves disposed of related to the divestiture of the Canadian business (1,627)  
Unrealized foreign exchange (gain) loss (39) 204
Net reserves at end of period 60,340 59,714
Reinsurance recoverables on unpaid losses 7,787 7,987
Claims and claim adjustment expense reserves at end of period 68,127 $ 67,701
Amount of increase in gross claims and claim adjustment expense reserves 2,390  
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 3  
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)