COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) (USD $)	9 Months Ended
	Jun. 30, 2014
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 96,900,000
Natural Gas Purchases and Future Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	330,902,000	[1]
2015	457,821,000	[1]
2016	129,780,000	[1]
2017	75,155,000	[1]
2018	83,627,000	[1]
Thereafter	556,707,000	[1]
NJRES [Member] | Natural Gas Purchases [Member]
Long-term Purchase Commitment [Line Items]
2014	252,840,000
2015	179,692,000
2016	15,790,000
2017	0
2018	0
Thereafter	0
NJRES [Member] | Storage Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	8,812,000
2015	26,813,000
2016	10,363,000
2017	5,608,000
2018	3,500,000
Thereafter	4,381,000
NJRES [Member] | Pipeline Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	19,061,000
2015	45,117,000
2016	34,142,000
2017	18,221,000
2018	12,541,000
Thereafter	7,173,000
NJRES [Member] | Natural Gas Purchases and Future Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	280,713,000
2015	251,622,000
2016	60,295,000
2017	23,829,000
2018	16,041,000
Thereafter	11,554,000
NJRES [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	1 year
NJRES [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Storage and pipeline capacity, contract term	10 years
NJNG [Member] | Natural Gas Purchases [Member]
Long-term Purchase Commitment [Line Items]
2014	27,690,000
2015	106,985,000
2016	5,937,000
2017	113,000
2018	0
Thereafter	0
NJNG [Member] | Storage Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	6,498,000
2015	24,045,000
2016	17,865,000
2017	10,883,000
2018	9,299,000
Thereafter	13,948,000
NJNG [Member] | Pipeline Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	16,001,000
2015	75,169,000
2016	45,683,000
2017	40,330,000
2018	58,287,000
Thereafter	531,205,000
NJNG [Member] | Natural Gas Purchases and Future Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	50,189,000
2015	206,199,000
2016	69,485,000
2017	51,326,000
2018	67,586,000
Thereafter	$ 545,153,000

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