Benefit Plans - Weighted Average Assumptions Determining Pension Plan (Detail) - Pension Plans	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Foreign Plans
Net Cost
Discount rate	1.44%	1.39%	2.30%
Expected return on plan assets	4.92%	5.05%	4.98%
Rate of compensation increase	2.20%	2.35%	2.36%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1.95%	1.97%	1.84%
Benefit Obligation
Discount rate	1.75%	1.44%	1.39%
Rate of compensation increase	2.63%	2.20%	2.35%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	2.02%	1.95%	1.97%
United States
Net Cost
Discount rate	2.80%	3.21%	4.26%
Expected return on plan assets	6.25%	7.25%	7.25%
Rate of compensation increase	4.30%	4.29%	4.29%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	4.00%	4.00%	4.00%
Benefit Obligation
Discount rate	2.89%	2.80%	3.21%
Rate of compensation increase	4.31%	4.30%	4.29%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	4.00%	4.00%	4.00%

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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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

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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.

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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.

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920

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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

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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

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