DERIVATIVE INSTRUMENTS - VOLUME (Details) $ in Millions	Sep. 30, 2018 USD ($) Bcf certificate	Sep. 30, 2017 Bcf
Foreign currency contracts
Derivative [Line Items]
Derivative, notional amount \| $	$ 8.5
Natural Gas Distribution \| Long \| Futures
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	27.9	18.2
Natural Gas Distribution \| Long \| Physical
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	23.1	32.1
Energy Services \| Physical commodity contracts
Derivative [Line Items]
Number of Solar Renewable Energy Certificates (in certificates) \| certificate	(698,700)
Energy Services \| Short \| Futures
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	(7.0)	(16.4)
Energy Services \| Short \| Physical
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	51.2	(13.1)

- Definition

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

+ References

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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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

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

+ Details

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- Definition

Number of Solar Renewable Energy Certificates

+ References

No definition available.

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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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