DERIVATIVE INSTRUMENTS - VOLUME (Details)	Dec. 31, 2013 MMcf	Sep. 30, 2013 MMcf
NJNG [Member] | Futures [Member] | Long Position [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	24,500	22,600
NJRES [Member] | Futures [Member] | Short Position [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	(73,000)	(64,200)
NJRES [Member] | Options [Member] | Long Position [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	900	1,500
NJRES [Member] | Forward Contracts [Member] | Long Position [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	13,900	7,300