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Benefit Plans Asset Holdings (Details) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure
Target Allocation	100.00%
Plan Asset Allocations	100.00%	100.00%
Global public equity
Defined Benefit Plan Disclosure
Target Allocation	32.00%
Plan Asset Allocations	36.00%	37.00%
Public real assets
Defined Benefit Plan Disclosure
Target Allocation	10.00%
Plan Asset Allocations	10.00%	15.00%
Private equity
Defined Benefit Plan Disclosure
Target Allocation	8.00%
Plan Asset Allocations	13.00%	10.00%
Safety oriented fixed income
Defined Benefit Plan Disclosure
Target Allocation	20.00%
Plan Asset Allocations	18.00%	18.00%
Opportunistic fixed income
Defined Benefit Plan Disclosure
Target Allocation	20.00%
Plan Asset Allocations	15.00%	12.00%
Private real assets
Defined Benefit Plan Disclosure
Target Allocation	10.00%
Plan Asset Allocations	8.00%	8.00%
Other Post-retirement Benefits
Defined Benefit Plan Disclosure
Actuarial assumption COLA	$ 1.54	$ 0.0221	$ 0.0184

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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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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.

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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)
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