DERIVATIVE INSTRUMENTS - VOLUME (Details) $ in Millions	Jun. 30, 2015 USD ($) Bcf		Jun. 01, 2015 USD ($)	Sep. 30, 2014 Bcf
Derivative [Line Items]
Notional amount related to treasury lock agreement | $	$ 125		$ 125
NJNG [Member] | Futures [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount (in bcf)	26.2	[1]		17.3
NJRES [Member] | Futures [Member] | Short [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount (in bcf)	(57.4)			(62.1)
NJRES [Member] | Options [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount (in bcf)	1.2			1.2
NJRES [Member] | Physical [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount (in bcf)	58.4			28.6

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