Employee Benefit Plans - Assumptions Used to Determine Pension Benefit Obligations and Periodic Benefit Costs, Postretirement Benefit Obligations and Net Costs (Detail)		12 Months Ended
		Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate		6.00%		5.50%	2.20%
Initial health care cost trend rate				3.00%
Cash balance interest credit rate		2.00%		2.00%	2.00%
Discount rate - benefit obligation		5.60%		2.20%	2.50%
Discount rate - interest cost		5.30%		1.60%	1.40%
Cash balance interest credit rate		2.00%		2.00%	2.10%
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate		4.70%		4.50%	2.10%
Initial health care cost trend rate		3.00%		3.00%	2.90%
Cash balance interest credit rate		2.10%		2.00%	1.70%
Discount rate - benefit obligation		4.50%		2.10%	1.70%
Discount rate - service cost		3.60%		2.00%	1.70%
Discount rate - interest cost		4.50%		1.70%	1.40%
Expected long-term rate of return on plan assets		5.10%		3.50%	4.60%
Initial health care cost trend rate		3.00%		2.90%	3.00%
Cash balance interest credit rate		2.00%		1.70%	1.70%
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	[1]	6.00%		5.60%	2.40%
Initial health care cost trend rate		5.00%	[1]	0.00%	5.50%	[1]
Discount rate - benefit obligation	[1]	5.60%		2.40%	2.10%
Discount rate - service cost	[1]	5.40%		1.70%	1.50%
Discount rate - interest cost	[1]	5.30%		1.60%	1.40%
Initial health care cost trend rate	[1]			5.50%	6.00%
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	[1]	5.70%		5.10%	2.80%
Initial health care cost trend rate	[1]	6.40%		6.80%	6.90%
Discount rate - benefit obligation	[1]	5.10%		2.80%	2.40%
Discount rate - service cost	[1]	5.10%		3.50%	3.00%
Discount rate - interest cost	[1]	5.10%		2.50%	2.10%
Initial health care cost trend rate	[1]	6.80%		6.90%	6.90%

[1] The initial health care cost trend rate is set at 5% for the 2023 U.S. plan assumptions as the 2024 Medicare Part B premiums are expected to increase. The trend rates for all future years beyond 2024 also reflect expected 5% increases. The initial health care cost trend rate was set at zero for the 2022 U.S. plan assumptions in light of the expected downward adjustment the U.S. government was expected to make to the 2023 Medicare Part B premiums, however, all trend rates beyond the initial year were set to 5%