v3.26.3
Retirement Benefits - Defined Benefit Plan Change in Fair Value of Plan Assets Level Three (Details) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year $ 2,810  
Plan assets at end of year 2,488 $ 2,810
Level 3    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year 74 74
Realized Gains (Losses) 0 0
Unrealized Gains (Losses) (6) 2
Purchases, Sales, Issuances, and Settlements, Net 0 (2)
Plan assets at end of year 68 74
Non-U.S. Plans    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year 989  
Plan assets at end of year 983 989
Non-U.S. Plans | Level 3    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year 74  
Plan assets at end of year 68 74
Non-U.S. Plans | Level 3 | Insurance contracts    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year 73 72
Realized Gains (Losses) 0 0
Unrealized Gains (Losses) (6) 2
Purchases, Sales, Issuances, and Settlements, Net (1) (1)
Plan assets at end of year 66 73
Non-U.S. Plans | Level 3 | Other    
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]    
Plan assets at beginning of year 1 2
Realized Gains (Losses) 0 0
Unrealized Gains (Losses) 0 0
Purchases, Sales, Issuances, and Settlements, Net 1 (1)
Plan assets at end of year $ 2 $ 1