DERIVATIVE INSTRUMENTS - BROKER MARGIN DEPOSITS (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Derivative [Line Items]
Broker margin - Current assets	$ 34,156	$ 12,990
Broker margin - Current (liabilities)	(12,798)	(4,103)
NJNG [Member]
Derivative [Line Items]
Broker margin - Current assets	20,235	12,990
NJRES [Member]
Derivative [Line Items]
Broker margin - Current assets	13,921	0
Broker margin - Current (liabilities)	$ (12,798)	$ (4,103)