v3.25.2
Benefit Plans Components of Benefit Plans (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Pension Plan        
Retirement Plan Disclosure        
Service cost $ 8 $ 7 $ 24 $ 22
Interest cost 131 145 394 434
Defined Benefit Plan, Expected Return (Loss) on Plan Assets (126) 123 (379) 370
Amortization of prior service cost (22) (22) (67) (67)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 44 (25) 131 (75)
Net periodic benefit cost as acutarially determined 35 32 103 94
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 35 32 103 94
Other Postretirement Benefit Plan        
Retirement Plan Disclosure        
Service cost 3 3 9 8
Interest cost 3 4 12 15
Defined Benefit Plan, Expected Return (Loss) on Plan Assets 0 0 0 0
Amortization of prior service cost (4) (4) (13) (13)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 0 0 0 0
Net periodic benefit cost as acutarially determined 3 3 9 10
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 2 3 8 10
Defined benefit plan contributions     19  
Other Pension Plan        
Retirement Plan Disclosure        
Defined benefit plan contributions     225  
401K [Member]        
Retirement Plan Disclosure        
Defined benefit plan contributions     95  
Special Termination Benefits        
Retirement Plan Disclosure        
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 0 $ 0 0 $ 0
Postemployment Retirement Benefits        
Retirement Plan Disclosure        
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) $ 1   $ 1