Retirement Plans - Components and Assumptions of Net Periodic Benefit Cost (Credit) (Details) - Pension plan - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 8	$ 7	$ 7
Interest cost	9	10	13
Expected return on plan assets	(18)	(19)	(18)
Net actuarial (gain) loss	(15)	22	49
Settlement (gain) loss	0	1	2
Net periodic benefit cost (credit)	$ (16)	$ 21	$ 53
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	2.91%	3.34%	4.29%
Expected return on plan assets	5.75%	5.75%	5.00%
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	1.70%	1.85%	2.71%
Expected return on plan assets	3.68%	4.01%	4.08%
Rate of compensation increase	4.15%	3.66%	3.46%