DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
Derivatives, Fair Value [Line Items]
Derivative assets, current	$ 60,013us-gaap_DerivativeAssetsCurrent	$ 64,223us-gaap_DerivativeAssetsCurrent
Derivative liabilities, current	84,626us-gaap_DerivativeLiabilitiesCurrent	79,863us-gaap_DerivativeLiabilitiesCurrent
Derivative assets, noncurrent	5,141us-gaap_DerivativeAssetsNoncurrent	5,654us-gaap_DerivativeAssetsNoncurrent
Derivative liabilities, noncurrent	3,598us-gaap_DerivativeLiabilitiesNoncurrent	6,690us-gaap_DerivativeLiabilitiesNoncurrent
Derivative assets	65,154us-gaap_DerivativeAssets	69,877us-gaap_DerivativeAssets
Derivative liabilities	88,224us-gaap_DerivativeLiabilities	86,553us-gaap_DerivativeLiabilities
Notional amount of foreign currency derivatives	101invest_DerivativeNotionalAmount
Designated as Hedging Instrument [Member] \| NJRES [Member] \| Foreign Currency Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, current	0	0
Derivative liabilities, current	18	155
Derivative assets	0	0
Derivative liabilities	18	155
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	65,154	69,877
Derivative liabilities	88,206	86,398
Not Designated as Hedging Instrument [Member] \| NJRES [Member] \| Financial Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, current	48,725	46,307
Derivative liabilities, current	47,442	46,725
Derivative assets, noncurrent	4,446	5,537
Derivative liabilities, noncurrent	3,598	6,533
Not Designated as Hedging Instrument [Member] \| NJRES [Member] \| Physical Forward Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, current	10,381	15,391
Derivative liabilities, current	11,521	30,778
Derivative assets, noncurrent	695	35
Derivative liabilities, noncurrent	0	132
Not Designated as Hedging Instrument [Member] \| NJNG [Member] \| Financial Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, current	907	2,525
Derivative liabilities, current	25,645	2,205
Derivative assets, noncurrent	0	82
Derivative liabilities, noncurrent	$ 0	$ 25

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

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-Number 210

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-Section 13

-Sentence Column B

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