Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Percent of total assets domestic plans		68.00%
Cost of the savings incentive plan		$ 153	$ 111	$ 126
Fixed Income Funds
Defined Benefit Plan Disclosure [Line Items]
Company's Target allocation percentage for asset mix		45.00%
Diversified
Defined Benefit Plan Disclosure [Line Items]
Company's Target allocation percentage for asset mix		23.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Company's Target allocation percentage for asset mix		32.00%
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value		$ 3,222	3,045	2,926
Pension plan projected benefit obligations		3,889	3,953	$ 3,731
Employer contribution		66	42
Foreign Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value		1,033	935
Pension plan projected benefit obligations		$ 1,320	1,321
Percent of total plan assets foreign plans		32.00%
Foreign Plans | Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value		$ 297	335
United States | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value		2,189	2,108
Employer contribution		16
United States | Pension Plans | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	$ 134
United States | Pension Plans | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value		686	737
United States | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan projected benefit obligations		$ 138	$ 148