DERIVATIVE INSTRUMENTS - VOLUME (Details)	Jun. 30, 2016 Bcf certificate	Sep. 30, 2015 Bcf
NJNG [Member] | Long [Member] | Futures [Member]
Derivative [Line Items]
Volume	14.6	25.8
NJNG [Member] | Long [Member] | Physical [Member]
Derivative [Line Items]
Volume	3.5	0.0
NJRES [Member] | Physical Commodity Contracts [Member]
Derivative [Line Items]
Number of SRECs | certificate	142,500
NJRES [Member] | Long [Member] | Physical [Member]
Derivative [Line Items]
Volume	123.7	48.2
NJRES [Member] | Long [Member] | Options [Member]
Derivative [Line Items]
Volume	5.7	1.2
NJRES [Member] | Short [Member] | Futures [Member]
Derivative [Line Items]
Volume	97.6	91.1