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Employee Benefit Plans - Assumptions Used to Determine Pension Benefit Obligations and Periodic Benefit Costs, Postretirement Benefit Obligations and Net Costs (Detail) | 12 Months Ended
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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%

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- Definition Defined benefit plan assumptions used calculating net periodic benefit cost discount rate interest cost. + References No definition available. + Details
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- Definition Defined benefit plan assumptions used calculating net periodic benefit cost discount rate service cost. + References No definition available. + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted-average interest crediting rate used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-8 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(3) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Weighted-average interest crediting rate used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, cash balance and other defined benefit plans with promised interest crediting rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k)(4) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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