v3.25.2
U.S. and Europe Retrospective Responsibility Plans - Schedule of Changes in Preferred Stock and Right to Recover Covered Losses (Details)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2025
USD ($)
$ / shares
shares
Jun. 30, 2024
USD ($)
shares
Jun. 30, 2025
USD ($)
$ / shares
shares
Jun. 30, 2024
USD ($)
shares
Mar. 31, 2025
shares
Sep. 30, 2024
USD ($)
$ / shares
shares
Mar. 31, 2024
shares
Sep. 30, 2023
shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Balance as of beginning of period $ 38,030 $ 40,485 $ 39,137 $ 38,733        
VE territory covered losses 2 (21) (22) (81)        
Recovery through conversion rate adjustment   (6) 0 (6)        
Balance as of end of period 38,664 39,729 38,664 39,729        
As-converted Value of Preferred Stock 2,875   2,875     $ 2,234    
Book value of preferred stock 871   871     1,031    
Book Value of Preferred Stock, Total 483   483     491    
Less: right to recover for covered losses (118)   (118)     (104)    
As-converted Value of Preferred Stock, Total recovery for covered losses available 2,757   2,757     2,130    
Book Value of Preferred of Stock, Total recovery for covered losses available $ 365   $ 365     $ 387    
Preferred stock, shares outstanding (in shares) | shares 5   5     5    
Share price (in dollars per share) | $ / shares $ 355.05   $ 355.05     $ 274.95    
Preferred Stock                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Balance as of beginning of period $ 880 1,602 $ 1,031 [1] 1,698 [2]        
Recovery through conversion rate adjustment   (156) (8) (181)        
Balance as of end of period $ 871 [1] $ 1,425 [2] $ 871 [1] $ 1,425 [2]        
Preferred stock, shares outstanding (in shares) | shares 5 5 5 5 5 5 5 5
Right to Recover for Covered Losses                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Balance as of beginning of period $ (120) $ (175) $ (104) $ (140)        
VE territory covered losses 2 (21) (22) (81)        
Recovery through conversion rate adjustment   150 8 175        
Balance as of end of period (118) (46) (118) (46)        
Series B preferred stock                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Recovery through conversion rate adjustment     5 161        
As-converted Value of Preferred Stock 877   877     $ 684    
Book value of preferred stock $ 99   $ 99     $ 104    
Preferred stock, shares outstanding (in shares) | shares 2   2     2    
Preferred stock, conversion rate 0.9960   0.9960     1.0030    
Series B preferred stock | Preferred Stock                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Balance as of beginning of period     $ 104 441        
VE territory covered losses     0 0        
Recovery through conversion rate adjustment     (5) (161)        
Balance as of end of period $ 99 280 99 280        
Series C preferred stock                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Recovery through conversion rate adjustment     3 20        
As-converted Value of Preferred Stock 1,998   1,998     $ 1,550    
Book value of preferred stock $ 384   $ 384     $ 387    
Preferred stock, shares outstanding (in shares) | shares 3   3     3    
Preferred stock, conversion rate 1.7830   1.7830     1.7860    
Series C preferred stock | Preferred Stock                
Increase (Decrease) in Stockholders' Equity [Roll Forward]                
Balance as of beginning of period     $ 387 801        
VE territory covered losses     0 0        
Recovery through conversion rate adjustment     (3) (20)        
Balance as of end of period $ 384 $ 781 $ 384 $ 781        
[1] As of June 30, 2025 and September 30, 2024, the book value of series A convertible participating preferred stock (series A preferred stock) was $388 million and $540 million, respectively. See Note 5—U.S. and Europe Retrospective Responsibility Plans for the book value of series B convertible participating preferred stock (series B preferred stock) and series C convertible participating preferred stock (series C preferred stock).
[2] As of June 30, 2024 and September 30, 2023, the book value of series A preferred stock was $364 million and $456 million, respectively. See Note 5—U.S. and Europe Retrospective Responsibility Plans for the book value of series B and series C preferred stock.