DERIVATIVE INSTRUMENTS - VOLUME (Details)	Dec. 31, 2014 MMcf	Sep. 30, 2014 MMcf
NJNG [Member] | Futures [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	21,500	17,300
NJNG [Member] | Options [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	500	0
NJRES [Member] | Futures [Member] | Short [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	(83,200)	(62,100)
NJRES [Member] | Options [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	1,200	1,200
NJRES [Member] | Physical [Member] | Long [Member]
Derivative [Line Items]
Derivative, nonmonetary notional amount	67,600	28,600