DERIVATIVE INSTRUMENTS, OFFSETTING OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Sep. 30, 2014
NJRES [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	$ 44,870	$ 67,270
Offsetting Derivative Instruments	[2]	(15,060)	(63,375)
Financial Collateral Received/Pledged	[3]	3,841	0
Net Amounts	[4]	33,651	3,895
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	23,004	84,323
Offsetting Derivative Instruments	[2]	(15,059)	(63,902)
Financial Collateral Received/Pledged	[3]	(1,200)	(2,614)
Net Amounts	[4]	6,745	17,807
NJRES [Member] | Physical Forward Commodity Contracts [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	6,562	15,426
Offsetting Derivative Instruments	[2]	(1,326)	(11,531)
Financial Collateral Received/Pledged	[3]	0	0
Net Amounts	[4]	5,236	3,895
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	9,271	30,910
Offsetting Derivative Instruments	[2]	(1,326)	(12,058)
Financial Collateral Received/Pledged	[3]	(1,200)	(1,200)
Net Amounts	[4]	6,745	17,652
NJRES [Member] | Financial Commodity Contracts [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	38,308	51,844
Offsetting Derivative Instruments	[2]	(13,734)	(51,844)
Financial Collateral Received/Pledged	[3]	3,841	0
Net Amounts	[4]	28,415	0
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	13,733	53,258
Offsetting Derivative Instruments	[2]	(13,733)	(51,844)
Financial Collateral Received/Pledged	[3]	0	(1,414)
Net Amounts	[4]	0	0
NJRES [Member] | Foreign Currency Contracts [Member]
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]		155
Offsetting Derivative Instruments	[2]		0
Financial Collateral Received/Pledged	[3]		0
Net Amounts	[4]		155
NJNG [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	207
Offsetting Derivative Instruments	[2]	(207)
Financial Collateral Received/Pledged	[3]	0
Net Amounts	[4]	0
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	15,316	2,230
Offsetting Derivative Instruments	[2]	(207)	(2,230)
Financial Collateral Received/Pledged	[3]	(10,881)	0
Net Amounts	[4]	4,228	0
NJNG [Member] | Financial Commodity Contracts [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	207	2,607
Offsetting Derivative Instruments	[2]	(207)	(2,230)
Financial Collateral Received/Pledged	[3]	0	(377)
Net Amounts	[4]	0	$ 0
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	11,088
Offsetting Derivative Instruments	[2]	(207)
Financial Collateral Received/Pledged	[3]	(10,881)
Net Amounts	[4]	0
NJNG [Member] | Interest Rate Contract [Member]
Derivative assets:
Amounts Presented on the Balance Sheets	[1]	0
Offsetting Derivative Instruments	[2]	0
Financial Collateral Received/Pledged	[3]	0
Net Amounts	[4]	0
Derivative liabilities:
Amounts Presented in Balance Sheets	[1]	4,228
Offsetting Derivative Instruments	[2]	0
Financial Collateral Received/Pledged	[3]	0
Net Amounts	[4]	$ 4,228

[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 FCMs with net margining and transactions with ISDA netting.

[3] Financial collateral includes cash balances at FCMs, 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.