v3.21.2
Pension and Other Postretirement Benefits - Net Periodic Pension and Other Postretirement Plan Cost (Detail) - USD ($)
$ in Millions
 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2019
U.S. Plans      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Service cost $ 0 $ 0 $ 0
Interest cost 25 28 32
Expected return on assets (70) (72) (71)
Amortization of actuarial (gain) loss 3 6 0
Settlement (gain) loss (1) 8 7
Total net periodic benefit cost (43) (30) (32)
Non-U.S. Plans      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Service cost 4 4 4
Interest cost 10 10 13
Expected return on assets (17) (15) (18)
Amortization of actuarial (gain) loss 4 2 0
Settlement (gain) loss 2 0 0
Total net periodic benefit cost $ 3 $ 1 $ (1)