SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, GAS IN STORAGE (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 MMcf	Sep. 30, 2012 MMcf
Public Utilities, Inventory [Line Items]
Gas in storage	$ 314,477	$ 265,193
Gas in storage (BCF)	82,700	67,700
NJNG [Member]
Public Utilities, Inventory [Line Items]
Gas in storage	104,979	145,379
Gas in storage (BCF)	20,400	22,200
NJRES [Member]
Public Utilities, Inventory [Line Items]
Gas in storage	$ 209,498	$ 119,814
Gas in storage (BCF)	62,300	45,500