COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	3 Months Ended
Dec. 31, 2016 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 60,900
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	457,957
2018	270,387
2019	182,326
2020	115,979
2021	103,644
Thereafter	748,264
NJRES
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	321,348
2018	149,179
2019	70,556
2020	12,179
2021	8,326
Thereafter	5,150
NJRES \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	239,269
2018	101,247
2019	51,731
2020	0
2021	0
Thereafter	0
NJRES \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	25,935
2018	19,079
2019	12,064
2020	9,248
2021	5,914
Thereafter	3,734
NJRES \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	56,144
2018	28,853
2019	6,761
2020	2,931
2021	2,412
Thereafter	$ 1,416
NJRES \| Minimum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	1 year
NJRES \| Maximum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	10 years
NJNG
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	$ 136,609
2018	121,208
2019	111,770
2020	103,800
2021	95,318
Thereafter	743,114
NJNG \| Natural gas purchases
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	75,679
2018	4,511
2019	0
2020	0
2021	0
Thereafter	0
NJNG \| Storage demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	21,865
2018	25,766
2019	19,864
2020	12,802
2021	7,023
Thereafter	10,535
NJNG \| Pipeline demand fees
Natural Gas Purchases and Future Demand Fees, Next Five Fiscal Years
2017	39,065
2018	90,931
2019	91,906
2020	90,998
2021	88,295
Thereafter	$ 732,579

Current Charges Recoverable Through Basic Gas Supply Service as shown for the reporting period

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Storage and Pipeline Capacity, Term of Contract

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Minimum amount of purchase arrangement maturing after the fifth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the fourth fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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Minimum amount of purchase arrangement maturing in the third fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

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