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Retirement Benefits (Schedule of Assumptions Used) (Details) | 12 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Defined Benefit Pension Plan [Member] | UNITED STATES |  |  |
Weighted-average assumptions to determine benefit obligation at September 30: |  |  |
Discount rate | 3.80% | 3.65% | 4.39%
Weighted-average assumptions to determine periodic benefit costs for years ending September 30: |  |  |
Discount rate | 3.65% | 4.39% | 4.40%
Long-term rate of return on plan assets | 7.38% | 7.62% | 7.62%
Defined Benefit Pension Plan [Member] | UNITED KINGDOM |  |  |
Weighted-average assumptions to determine benefit obligation at September 30: |  |  |
Discount rate | 2.56% | 2.28% | 3.75%
Rate of compensation increase | 3.60% | 3.40% | 3.40%
Weighted-average assumptions to determine periodic benefit costs for years ending September 30: |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Service Cost | 2.33% | 3.86% | 4.10%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Interest Cost | 2.24% | 3.63% | 4.10%
Rate of compensation increase | 3.40% | 3.40% | 3.50%
Long-term rate of return on plan assets | 4.75% | 5.00% | 5.50%
Defined Benefit Pension Plan [Member] | JAPAN |  |  |
Weighted-average assumptions to determine benefit obligation at September 30: |  |  |
Discount rate | 0.58% | 0.46% | 0.97%
Rate of compensation increase | 2.00% | 2.02% | 2.00%
Weighted-average assumptions to determine periodic benefit costs for years ending September 30: |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Service Cost | 0.59% | 1.27% | 1.10%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Interest Cost | 0.45% | 0.59% | 1.10%
Rate of compensation increase | 2.02% | 2.00% | 2.00%
Long-term rate of return on plan assets | 2.50% | 3.00% | 3.00%
Other Postretirement Benefit Plans [Member] |  |  |
Weighted-average assumptions to determine benefit obligation at September 30: |  |  |
Discount rate | 3.78% | 3.63% | 4.01%
Weighted-average assumptions to determine periodic benefit costs for years ending September 30: |  |  |
Discount rate | 3.63% | 4.01% | 4.40%

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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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