DERIVATIVE INSTRUMENTS - VOLUME (Details)	Jun. 30, 2014 MMcf	Sep. 30, 2013 MMcf
NJNG [Member] | Futures [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	15,300	22,600
NJRES [Member] | Futures [Member] | Short [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	(59,300)	(64,200)
NJRES [Member] | Options [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	600	1,500
NJRES [Member] | Physical [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	33,000	7,300