Derivative Commodities and Disclosures (Details) MWh in Thousands, MMBTU in Thousands, Gallon in Thousands, $ in Millions	Sep. 30, 2017 USD ($) MMBTU Gallon MWh	Sep. 30, 2016 MMBTU Gallon MWh
Derivative
Derivatives in a net liability position	$ 1.3
Collateral Already Posted, Aggregate Fair Value	0.4
Additional Collateral, Aggregate Fair Value	$ 4.7
Electricity (MWh) \| Long
Derivative
Derivative, Nonmonetary Notional Amount \| MWh	122	130
Electricity (MWh) \| Short
Derivative
Derivative, Nonmonetary Notional Amount \| MWh	162	143
Natural Gas (MMBTU) \| Long
Derivative
Derivative, Nonmonetary Notional Amount \| MMBTU	7,975	7,977
Natural Gas (MMBTU) \| Short
Derivative
Derivative, Nonmonetary Notional Amount \| MMBTU	230	70
Diesel Fuel (Gallons) \| Long
Derivative
Derivative, Nonmonetary Notional Amount \| Gallon	304	267

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959

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