COMMITMENTS AND CONTINGENT LIABILITIES, SCHEDULE OF FUTURE COMMITTED EXPENSES (Details) (USD $)	12 Months Ended
	Sep. 30, 2013
Long-term Purchase Commitment [Line Items]
Current charges recoverable through BGSS	$ 96,000,000
2014	512,077,000	[1]
2015	227,634,000	[1]
2016	89,395,000	[1]
2017	56,884,000	[1]
2018	52,771,000	[1]
Thereafter	214,324,000	[1]
Natural Gas Purchases [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	238,843,000
2015	31,282,000
2016	15,513,000
2017	0
2018	0
Thereafter	0
Natural Gas Purchases [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	104,466,000
2015	100,487,000
2016	8,564,000
2017	113,000
2018	0
Thereafter	0
Storage Demand Fees [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	28,613,000
2015	12,017,000
2016	7,114,000
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	29,082,000
2015	22,158,000
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	44,277,000
2015	20,364,000
2016	10,046,000
2017	8,303,000
2018	6,983,000
Thereafter	2,783,000
Pipeline Demand Fees [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	66,796,000
2015	41,326,000
2016	35,762,000
2017	33,440,000
2018	33,171,000
Thereafter	193,593,000
Natural Gas Purchases and Future Demand Fees [Member] | NJRES [Member]
Long-term Purchase Commitment [Line Items]
2014	311,733,000
2015	63,663,000
2016	32,673,000
2017	13,338,000
2018	10,301,000
Thereafter	6,783,000
Natural Gas Purchases and Future Demand Fees [Member] | NJNG [Member]
Long-term Purchase Commitment [Line Items]
2014	200,344,000
2015	163,971,000
2016	56,722,000
2017	43,546,000
2018	42,470,000
Thereafter	$ 207,541,000

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