Retirement Plans - Reconciliations of Actuarial Present Value of Projected Benefit Obligations and Fair Value of Plan Assets for Defined Benefit Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Change in fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning	$ 4,533
Fair value of plan assets, ending	4,454	$ 4,533
U.S. Plans
Change in projected benefit obligation [Roll Forward]
Projected benefit obligation, beginning	3,112	4,338
Service cost	25	49	$ 54
Interest cost	164	99	94
Actuarial gain	(75)	(1,170)
Curtailments	(31)	0
Benefits paid	(204)	(204)
Settlements	(2)	0
Acquisitions (Divestitures), net	(56)	0
Foreign currency translation and other	1	0
Projected benefit obligation, ending	2,934	3,112	4,338
Change in fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning	3,625	4,844
Actual return on plan assets	230	(1,030)
Employer contributions	14	15
Benefits paid	(204)	(204)
Settlements	(2)	0
Acquisitions (Divestitures), net	(74)	0
Foreign currency translation and other	1	0
Fair value of plan assets, ending	3,590	3,625	4,844
Net amount recognized in the balance sheet	656	513
Noncurrent asset	815	663
Noncurrent asset held-for-sale	0	13
Current liability	(14)	(14)
Noncurrent liability	(145)	(149)
Net liability held-for-sale	0	0
Pretax accumulated other comprehensive loss	(257)	(284)
Non-U.S. Plans
Change in projected benefit obligation [Roll Forward]
Projected benefit obligation, beginning	965	1,562
Service cost	20	25	29
Interest cost	50	33	32
Actuarial gain	(25)	(404)
Curtailments	0	0
Benefits paid	(42)	(40)
Settlements	(70)	(29)
Acquisitions (Divestitures), net	(46)	0
Foreign currency translation and other	74	(182)
Projected benefit obligation, ending	926	965	1,562
Change in fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning	908	1,474
Actual return on plan assets	(40)	(337)
Employer contributions	32	28
Benefits paid	(42)	(40)
Settlements	(70)	(29)
Acquisitions (Divestitures), net	2	0
Foreign currency translation and other	74	(188)
Fair value of plan assets, ending	864	908	$ 1,474
Net amount recognized in the balance sheet	(62)	(57)
Noncurrent asset	180	205
Noncurrent asset held-for-sale	0	0
Current liability	(17)	(17)
Noncurrent liability	(225)	(203)
Net liability held-for-sale	0	(42)
Pretax accumulated other comprehensive loss	$ (181)	$ (136)