DERIVATIVE INSTRUMENTS - OFFSETTING OF ASSETS AND LIABILITIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Sep. 30, 2013
NJRES [Member]
Offsetting Assets and Liabilities [Line Items]
Amounts Presented in Balance Sheets, Derivative assets	$ 30,188	[1]	$ 52,465	[1]
Offsetting Derivative Instruments, Derivative assets	(26,330)	[2]	(29,617)	[2]
Financial Collateral Received/Pledged, Derivative assets	0	[3]	6,770	[3]
Net Amounts, Derivative assets	3,858	[4]	29,618	[4]
Amounts Presented in Balance Sheets, Derivative liabilities	83,943	[1]	40,663	[1]
Offsetting Derivative Instruments, Derivative liabilities	(26,330)	[2]	(29,617)	[2]
Financial Collateral Received/Pledged, Derivative liabilities	(33,851)	[3]	(500)	[3]
Net Amounts, Derivative liabilities	23,762	[4]	10,546	[4]
NJRES [Member] | Physical Forward Commodity Contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Amounts Presented in Balance Sheets, Derivative assets	9,055	[1]	11,823	[1]
Offsetting Derivative Instruments, Derivative assets	(5,197)	[2]	(3,549)	[2]
Financial Collateral Received/Pledged, Derivative assets	0	[3]	(100)	[3]
Net Amounts, Derivative assets	3,858	[4]	8,174	[4]
Amounts Presented in Balance Sheets, Derivative liabilities	29,415	[1]	14,595	[1]
Offsetting Derivative Instruments, Derivative liabilities	(5,197)	[2]	(3,549)	[2]
Financial Collateral Received/Pledged, Derivative liabilities	(500)	[3]	(500)	[3]
Net Amounts, Derivative liabilities	23,718	[4]	10,546	[4]
NJRES [Member] | Financial Commodity Contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Amounts Presented in Balance Sheets, Derivative assets	21,131	[1]	40,626	[1]
Offsetting Derivative Instruments, Derivative assets	(21,131)	[2]	(26,063)	[2]
Financial Collateral Received/Pledged, Derivative assets	0	[3]	6,870	[3]
Net Amounts, Derivative assets	0	[4]	21,433	[4]
Amounts Presented in Balance Sheets, Derivative liabilities	54,482	[1]	26,063	[1]
Offsetting Derivative Instruments, Derivative liabilities	(21,131)	[2]	(26,063)	[2]
Financial Collateral Received/Pledged, Derivative liabilities	(33,351)	[3]	0	[3]
Net Amounts, Derivative liabilities	0	[4]	0	[4]
NJRES [Member] | Foreign Currency Contract [Member]
Offsetting Assets and Liabilities [Line Items]
Amounts Presented in Balance Sheets, Derivative assets	2	[1]	16	[1]
Offsetting Derivative Instruments, Derivative assets	(2)	[2]	(5)	[2]
Financial Collateral Received/Pledged, Derivative assets	0	[3]	0	[3]
Net Amounts, Derivative assets	0	[4]	11	[4]
Amounts Presented in Balance Sheets, Derivative liabilities	46	[1]	5	[1]
Offsetting Derivative Instruments, Derivative liabilities	(2)	[2]	(5)	[2]
Financial Collateral Received/Pledged, Derivative liabilities	0	[3]	0	[3]
Net Amounts, Derivative liabilities	44	[4]	0	[4]
NJNG [Member] | Financial Commodity Contracts [Member]
Offsetting Assets and Liabilities [Line Items]
Amounts Presented in Balance Sheets, Derivative assets	6,586	[1]	3,623	[1]
Offsetting Derivative Instruments, Derivative assets	(39)	[2]	(2,185)	[2]
Financial Collateral Received/Pledged, Derivative assets	(5,987)	[3]	214	[3]
Net Amounts, Derivative assets	560	[4]	1,652	[4]
Amounts Presented in Balance Sheets, Derivative liabilities	39	[1]	2,185	[1]
Offsetting Derivative Instruments, Derivative liabilities	(39)	[2]	(2,185)	[2]
Financial Collateral Received/Pledged, Derivative liabilities	0	[3]	0	[3]
Net Amounts, Derivative liabilities	$ 0	[4]	$ 0	[4]

[1] Derivative assets and liabilities are presented on a gross basis in the balance sheet as the Company does not elect balance sheet offsetting under ASC 210-20.

[2] Offsetting derivative instruments include: transactions with NAESB netting election, transactions held by FCM's with net margining and transactions with ISDA netting.

[3] Financial collateral includes cash balances at FCM's as well as cash received from or pledged to other counterparties.

[4] Net amounts represent presentation of derivative assets and liabilities if the Company were to elect balance sheet offsetting under ASC 210-20.