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Pension Benefit Obligations - Target Allocation and Plan Assets (Details)	Sep. 30, 2018	Sep. 30, 2017
United States
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	100.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	100.00%	100.00%
United States | Equity securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	40.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	40.00%	43.00%
United States | Debt
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	51.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	50.00%	47.00%
United States | Cash and cash equivalents
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	1.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	1.00%	1.00%
United States | Property And Other
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	8.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	9.00%	9.00%
Foreign Pension Plan, Defined Benefit
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	100.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	100.00%	100.00%
Foreign Pension Plan, Defined Benefit | Equity securities
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	25.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	38.00%	27.00%
Foreign Pension Plan, Defined Benefit | Debt
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	35.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	36.00%	38.00%
Foreign Pension Plan, Defined Benefit | Cash and cash equivalents
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	10.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	7.00%	2.00%
Foreign Pension Plan, Defined Benefit | Property And Other
Target Allocations by Asset Category
Target Allocations by Asset Category (as a percent)	30.00%
Percentage of Plan Assets by Category
Plan Assets by Asset Category (as a percent)	19.00%	33.00%

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one 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 (d)(5)(i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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