SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, DEMAND FEES (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Demand fees	$ 218.8	$ 211.1	$ 214.0
NJRES
Demand fees	141.0	130.6	122.0
NJNG
Demand fees	$ 77.8	$ 80.5	$ 92.0
Minimum
Storage and pipeline capacity, contract term	1 year
Maximum
Storage and pipeline capacity, contract term	10 years