DERIVATIVE INSTRUMENTS, VOLUME (Details) $ in Millions	Sep. 30, 2015 USD ($) Bcf		Jun. 01, 2015 USD ($)	Sep. 30, 2014 Bcf
Derivative [Line Items]
Notional amount | $			$ 125
Treasury Lock [Member]
Derivative [Line Items]
Notional amount | $	$ 125
NJNG [Member] | Futures [Member] | Long Position [Member]
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	25.8	[1]		17.3
NJRES [Member] | Futures [Member] | Short Position [Member]
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	(91.1)			(62.1)
NJRES [Member] | Financial Options [Member] | Long Position [Member]
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	1.2			1.2
NJRES [Member] | Physical [Member] | Long Position [Member]
Derivative [Line Items]
Outstanding long (short) derivatives (in Bcf)	48.2			28.6

[1] Not included is the notional amount of $125 million related to NJNG’s treasury lock agreement.