Retirement Benefits - Schedule of Significant Assumptions Used in Determining Benefit Obligations (Details)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Expected gross health care cost trend rate in 2020	5.00%	0.00%
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Expected gross health care cost trend rate in 2020	5.50%
Pension Benefits \| U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.30%	4.35%	3.90%
Compensation increase rate	3.40%	3.50%
Health care cost trend rate	0.00%	0.00%
Pension Benefits \| Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.60%	2.48%
Compensation increase rate	3.06%	3.02%
Health care cost trend rate	0.00%	0.00%
Other Postretirement Benefits \| U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.90%	4.15%
Compensation increase rate	0.00%	0.00%
Health care cost trend rate	6.50%	6.50%
Other Postretirement Benefits \| Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.65%	3.30%
Compensation increase rate	0.00%	0.00%
Health care cost trend rate	4.50%	4.50%

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
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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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-Publisher FASB
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 715
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-Section 50
-Paragraph 1
-Subparagraph (l)
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Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

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