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DERIVATIVE INSTRUMENTS - CREDIT RISK EXPOSURE (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015
Credit Risk Exposure [Line Items]
Derivative, net liability position, aggregate fair value	$ 1,900	$ 4,200
Additional collateral, aggregate fair value	1,900	$ 4,200
NJNG [Member]
Credit Risk Exposure [Line Items]
Gross Credit Exposure	139,420
NJNG [Member] | Investment Grade [Member]
Credit Risk Exposure [Line Items]
Gross Credit Exposure	99,405
NJNG [Member] | Noninvestment Grade [Member]
Credit Risk Exposure [Line Items]
Gross Credit Exposure	9,693
NJNG [Member] | Internally Rated Investment Grade [Member]
Credit Risk Exposure [Line Items]
Gross Credit Exposure	22,507
NJNG [Member] | Internally Rated Noninvestment Grade [Member]
Credit Risk Exposure [Line Items]
Gross Credit Exposure	$ 7,815

X

- Definition

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=56946850&loc=SL5624258-113959

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- Definition

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13537-108611

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- Definition

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=56946850&loc=SL5624258-113959

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