Benefit Plans - Change in Benefit Obligation, Change in Fair Value of Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Amounts recognized in the Consolidated Balance Sheets at September 30:
Long-term Employee Benefit Obligations	$ (1,228)	$ (1,435)
Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning obligation	3,953	3,731
Service cost	150	153	$ 134
Interest cost	71	84	107
Plan amendments	30	0
Benefits paid	(156)	(186)
Impact of acquisitions	0	10
Actuarial (gain) loss	(69)	104
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement and Curtailment	49
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement		(17)
Other, includes translation	(19)	(74)
Ending obligation	3,889	3,953	3,731
Change in fair value of plan assets:
Beginning fair value	3,045	2,926
Actual return on plan assets	317	222
Employer contribution	66	42
Benefits paid	(156)	(186)
Impact of acquisitions	0	7
Settlements	(55)	(17)
Other, includes translation	5	51
Ending fair value	3,222	3,045	$ 2,926
Funded Status at September 30:
Unfunded benefit obligation	(667)	(908)
Amounts recognized in the Consolidated Balance Sheets at September 30:
Other	29	16
Salaries, wages and related items	(29)	(23)
Long-term Employee Benefit Obligations	(667)	(901)
Net amount recognized	(667)	(908)
Amounts recognized in Accumulated other comprehensive income (loss) before income taxes at September 30:
Prior service credit	41	31
Net actuarial loss	(972)	(1,281)
Net amount recognized	$ (931)	$ (1,250)