Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624177-113959

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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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DERIVATIVE INSTRUMENTS - INCOME STATEMENT RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Foreign currency contracts \| Gas purchases \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivatives (Effective Portion)		$ 8		$ (27)
Amount of Gain or (Loss) Reclassified from OCI into Income (Effective Portion)		(15)		27
Not Designated as Hedging Instrument \| NJRES
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ 22,246	(38,119)	$ 23,667	19,159
Not Designated as Hedging Instrument \| NJRES \| Physical commodity contracts \| Operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	1,364	3,997	8,089	24,999
Not Designated as Hedging Instrument \| NJRES \| Physical commodity contracts \| Gas purchases
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(1,131)	(2,463)	(13,912)	(29,283)
Not Designated as Hedging Instrument \| NJRES \| Financial commodity contracts \| Gas purchases
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	22,004	(39,653)	29,514	23,443
Not Designated as Hedging Instrument \| NJRES \| Foreign currency contracts \| Gas purchases
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	9	0	(24)	0
Not Designated as Hedging Instrument \| NJNG
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(8,736)	(4,999)	17,975	(39,018)
Not Designated as Hedging Instrument \| NJNG \| Physical commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(301)	(236)	(3,031)	(14,764)
Not Designated as Hedging Instrument \| NJNG \| Financial commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(4,232)	4,937	6,528	(5,849)
Not Designated as Hedging Instrument \| NJNG \| Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ (4,203)	$ (9,700)	$ 14,478	$ (18,405)