COMMITMENTS AND CONTINGENT LIABILITIES - SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) (USD $)	3 Months Ended
	Dec. 31, 2013
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 98,600,000
Natural Gas Purchases [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	337,533,000
2015	45,988,000
2016	15,357,000
2017	0
2018	0
Thereafter	0
Natural Gas Purchases [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	76,111,000
2015	90,929,000
2016	6,679,000
2017	113,000
2018	0
Thereafter	0
Storage Demand Fees [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	21,747,000
2015	13,819,000
2016	7,579,000
2017	5,035,000
2018	3,318,000
Thereafter	4,000,000
Storage Demand Fees [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	21,813,000
2015	22,163,000
2016	12,396,000
2017	9,993,000
2018	9,299,000
Thereafter	13,948,000
Pipeline Demand Fees [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	43,745,000
2015	26,671,000
2016	13,704,000
2017	11,965,000
2018	7,669,000
Thereafter	4,078,000
Pipeline Demand Fees [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	50,678,000
2015	71,145,000
2016	39,194,000
2017	34,229,000
2018	33,960,000
Thereafter	194,561,000
Natural Gas Purchases and Future Demand Fees [Member]
Long-term Purchase Commitment [Line Items]
2014	551,627,000	[1]
2015	270,715,000	[1]
2016	94,909,000	[1]
2017	61,335,000	[1]
2018	54,246,000	[1]
Thereafter	216,587,000	[1]
Natural Gas Purchases and Future Demand Fees [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	403,025,000
2015	86,478,000
2016	36,640,000
2017	17,000,000
2018	10,987,000
Thereafter	8,078,000
Natural Gas Purchases and Future Demand Fees [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	148,602,000
2015	184,237,000
2016	58,269,000
2017	44,335,000
2018	43,259,000
Thereafter	$ 208,509,000

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