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Benefit Plans Asset Holdings (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure
Target Allocation	100.00%
Plan Asset Allocations	100.00%	100.00%
Global public equity
Defined Benefit Plan Disclosure
New Policy Target Allocation	43.00%
Target Allocation	35.00%
Plan Asset Allocations	44.00%	44.00%
Fixed income
Defined Benefit Plan Disclosure
New Policy Target Allocation	32.00%
Public real assets
Defined Benefit Plan Disclosure
Target Allocation	15.00%
Plan Asset Allocations	15.00%	13.00%
Private equity
Defined Benefit Plan Disclosure
Target Allocation	8.00%
Plan Asset Allocations	7.00%	5.00%
Safety oriented fixed income
Defined Benefit Plan Disclosure
Target Allocation	17.00%
Plan Asset Allocations	16.00%	21.00%
Opportunistic fixed income
Defined Benefit Plan Disclosure
Target Allocation	15.00%
Plan Asset Allocations	10.00%	10.00%
Private real assets
Defined Benefit Plan Disclosure
New Policy Target Allocation	25.00%
Target Allocation	10.00%
Plan Asset Allocations	8.00%	7.00%

X

- Definition

New policy target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

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- Definition

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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=112275985&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=108410482&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=108410482&loc=d3e1928-114920

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