DEBT, NJNG SHORT-TERM DEBT (Details)	Sep. 26, 2014 USD ($)	May. 15, 2014 USD ($)		Apr. 23, 2014	Sep. 30, 2015 USD ($) debt_instrument	Sep. 30, 2014 USD ($)		Aug. 31, 2014 USD ($)	[1]
Line of Credit Facility [Line Items]
Debt instrument, term				3 years
NJNG [Member] | Letters of Credit [Member]
Line of Credit Facility [Line Items]
Number of debt instruments | debt_instrument					2
Letters of credit outstanding, amount					$ 731,000	$ 731,000
NJNG [Member] | Bank Revolving Credit Facilities [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity		$ 250,000,000	[1]			$ 250,000,000	[2]	$ 250,000,000
Debt instrument, term		5 years
Line of credit facility, maximum borrowing capacity, incremental increase		$ 15,000,000
Line of credit facility, maximum borrowing capacity, maximum increase		$ 50,000,000
NJNG [Member] | JPMC Term Loan [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000
Debt instrument, term	4 years

[1] Committed credit facilities, which require commitment fees of .075 percent and .1 percent on the unused amounts as of September 30, 2015 and 2014, respectively.

[2] Committed credit facilities, which require commitment fees of .075 percent on the unused amounts.