SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - GAS IN STORAGE (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014 MMcf	Sep. 30, 2013 MMcf
Inventory [Line Items]
Gas in Storage	$ 139,021	$ 314,477
Gas in Storage (Bcf)	25,300	82,700
NJNG [Member]
Inventory [Line Items]
Gas in Storage	12,582	104,979
Gas in Storage (Bcf)	2,100	20,400
NJRES [Member]
Inventory [Line Items]
Gas in Storage	$ 126,439	$ 209,498
Gas in Storage (Bcf)	23,200	62,300