SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, DEFERRED CHARGES (Details) (USD $) In Millions	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Demand Fees	$ 211.2	$ 203.7	$ 197.4
NJRES [Member]
Demand Fees	112.3	105.1	114.2
NJNG [Member]
Demand Fees	$ 98.9	$ 98.6	$ 83.2