DEBT - CREDIT FACILITIES (Details) (USD $)																				24 Months Ended		24 Months Ended
	Jun. 30, 2013 Commercial Paper [Member] NJNG [Member]	Sep. 30, 2012 Commercial Paper [Member] NJNG [Member]	Jun. 30, 2013 Notes Payable to Banks [Member] NJR [Member]	Sep. 30, 2012 Notes Payable to Banks [Member] NJR [Member]	Jun. 30, 2013 Letter of Credit [Member] NJR [Member]	Sep. 30, 2012 Letter of Credit [Member] NJR [Member]	Jun. 30, 2013 Letter of Credit [Member] NJR [Member]	Jun. 30, 2013 Bank Credit Facility Dedicated to EDA Bonds [Member] NJNG [Member]		Sep. 30, 2012 Bank Credit Facility Dedicated to EDA Bonds [Member] NJNG [Member]		Jun. 30, 2013 Bank Revolving Credit Facility [Member] NJNG [Member]		Sep. 30, 2012 Bank Revolving Credit Facility [Member] NJNG [Member]		Jun. 30, 2013 Bank Revolving Credit Facility [Member] NJR [Member]		Sep. 30, 2012 Bank Revolving Credit Facility [Member] NJR [Member]		May 10, 2013 Debt Shelf Facility Metlife [Member] NJR [Member]	Jun. 30, 2013 Debt Shelf Facility Metlife [Member] Unsecured senior note 1.94% [Member] NJR [Member]	Jun. 30, 2013 Debt Shelf Facility Prudential [Member] NJR [Member]
Line of Credit Facility [Line Items]
Bank credit facilities							$ 10,000,000	$ 100,000,000	[1],[2],[3]	$ 100,000,000	[1],[2],[3]	$ 250,000,000	[3]	$ 200,000,000	[3]	$ 325,000,000	[3]	$ 325,000,000	[3]			$ 75,000,000
Issuance period																				2 years		3 years
Amount outstanding at end of period	96,000,000	135,000,000	200,900,000	144,800,000																	25,000,000
Weighted average interest rate at end of period	0.15%	0.18%	1.12%	1.16%
Amount available at end of period												154,000,000		65,000,000		107,710,000	[4]	166,339,000	[4]			25,000,000
Letters of credit outstanding, amount					$ 16,400,000	$ 13,900,000

[1] There were no borrowings outstanding as of June 30, 2013 and September 30, 2012, respectively.

[2] New Jersey Economic Development Authority (EDA) Bonds.

[3] Committed credit facilities, which require commitment fees on the unused amounts.

[4] Letters of credit outstanding total $16.4 million and $13.9 million as of June 30, 2013 and September 30, 2012, respectively, which reduces amount available.