SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013 MMcf	Sep. 30, 2013 MMcf
Inventory [Line Items]
Gas in Storage	$ 283,356	$ 314,477
Gas in Storage (Bcf)	71,700	82,700
NJNG [Member]
Inventory [Line Items]
Gas in Storage	80,789	104,979
Gas in Storage (Bcf)	15,700	20,400
NJRES [Member]
Inventory [Line Items]
Gas in Storage	$ 202,567	$ 209,498
Gas in Storage (Bcf)	56,000	62,300