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Pension Benefit Obligations - Target Allocation and Plan Assets Allocations (Details)	Sep. 30, 2021	Sep. 30, 2020
United States
Percentage of Plan Assets:
Target allocations (as a percent)	100.00%
Plan assets (as a percent)	100.00%	100.00%
United States | Equities
Percentage of Plan Assets:
Target allocations (as a percent)	40.00%
Plan assets (as a percent)	41.00%	47.00%
United States | Debt.
Percentage of Plan Assets:
Target allocations (as a percent)	48.00%
Plan assets (as a percent)	44.00%	42.00%
United States | Cash and cash equivalents
Percentage of Plan Assets:
Target allocations (as a percent)	2.00%
Plan assets (as a percent)	5.00%	1.00%
United States | Property And Other
Percentage of Plan Assets:
Target allocations (as a percent)	10.00%
Plan assets (as a percent)	10.00%	10.00%
International
Percentage of Plan Assets:
Target allocations (as a percent)	100.00%
Plan assets (as a percent)	100.00%	100.00%
International | Equities
Percentage of Plan Assets:
Target allocations (as a percent)	34.00%
Plan assets (as a percent)	34.00%	26.00%
International | Debt.
Percentage of Plan Assets:
Target allocations (as a percent)	54.00%
Plan assets (as a percent)	53.00%	54.00%
International | Cash and cash equivalents
Percentage of Plan Assets:
Target allocations (as a percent)	2.00%
Plan assets (as a percent)	3.00%	4.00%
International | Property And Other
Percentage of Plan Assets:
Target allocations (as a percent)	10.00%
Plan assets (as a percent)	10.00%	16.00%

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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/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Percentage of actual 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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