COMMITMENTS AND CONTINGENT LIABILITIES, SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2016 USD ($)
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 85,600
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	499,483	[1]
2018	249,604	[1]
2019	170,845	[1]
2020	106,268	[1]
2021	94,463	[1]
Thereafter	735,787	[1]
NJRES
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	328,695
2018	132,853
2019	67,183
2020	10,561
2021	7,238
Thereafter	4,605
NJRES | Natural gas purchases
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	224,853
2018	91,807
2019	51,561
2020	0
2021	0
Thereafter	0
NJRES | Storage demand fees
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	34,674
2018	16,833
2019	9,924
2020	7,638
2021	4,834
Thereafter	3,194
NJRES | Pipeline demand fees
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	69,168
2018	24,213
2019	5,698
2020	2,923
2021	2,404
Thereafter	1,411
NJNG
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	170,788
2018	116,751
2019	103,662
2020	95,707
2021	87,225
Thereafter	731,182
NJNG | Natural gas purchases
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	85,196
2018	3,814
2019	0
2020	0
2021	0
Thereafter	0
NJNG | Storage demand fees
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	29,140
2018	22,265
2019	12,841
2020	5,779
2021	0
Thereafter	0
NJNG | Pipeline demand fees
Purchase Obligation, Fiscal Year Maturity [Abstract]
2017	56,452
2018	90,672
2019	90,821
2020	89,928
2021	87,225
Thereafter	$ 731,182
Minimum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, fixed period	1 year
Maximum
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, fixed period	10 years

[1] Does not include amounts related to intercompany asset management agreements between NJRES and NJNG.