DERIVATIVE INSTRUMENTS - VOLUME (Details) certificate in Thousands, $ in Millions	Sep. 30, 2019 USD ($) Bcf certificate	Sep. 30, 2018 Bcf
Foreign currency contracts
Derivative [Line Items]
Derivative, notional amount \| $	$ 6.2
Natural Gas Distribution \| Long \| Futures
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	27.6	27.9
Natural Gas Distribution \| Long \| Physical
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	11.6	23.1
Energy Services \| Physical commodity contracts
Derivative [Line Items]
Number of SRECs (in certificates) \| certificate	(796)
Energy Services \| Long \| Physical
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	44.5	51.2
Energy Services \| Short \| Futures
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	(29.6)	(7.0)

Number of Solar Renewable Energy Certificates

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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