SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, CAPITALIZED INTEREST (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Public Utilities, Allowance for Funds Used During Construction, Capitalized Interest	$ 1,020	$ 978	$ 748
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	2,100	2,165	568
AFUDC Weighted Average Rate	5.21%	7.39%	4.33%
Midstream Assets [Member]
Interest Costs, Capitalized During Period	0	0	1,909
Weighted Average Interest Rate	0.00%	0.00%	5.27%
NJNG [Member]
Interest Costs, Capitalized During Period	$ 3,120	$ 3,143	$ 3,225
Weighted Average Interest Rate	5.21%	7.39%	4.80%