DEBT, NJR LONG-TERM DEBT (Details) - NJR	Sep. 26, 2013 USD ($)	Sep. 30, 2016 USD ($) debt_instrument	Mar. 22, 2016	Sep. 30, 2015 USD ($)	Sep. 15, 2015 USD ($)	Nov. 07, 2014 USD ($)	Jul. 25, 2014 USD ($)	Jun. 30, 2014 USD ($)	May 10, 2013 USD ($)
Unsecured senior notes 3.25%
Debt Instrument [Line Items]
Long-term debt		$ 50,000,000		$ 50,000,000
Stated interest rate		3.25%
Unsecured senior notes 3.48%
Debt Instrument [Line Items]
Long-term debt		$ 100,000,000		100,000,000		$ 100,000,000
Stated interest rate		3.48%				3.48%
Unsecured Senior Notes
Debt Instrument [Line Items]
Number of debt instruments (in debt instruments) | debt_instrument		2
Unsecured Senior Notes 1.94%
Debt Instrument [Line Items]
Long-term debt					$ 25,000,000
Stated interest rate					1.94%
Unsecured senior notes 2.51%
Debt Instrument [Line Items]
Long-term debt		$ 25,000,000		25,000,000
Stated interest rate		2.51%
Unsecured senior notes 3.20%
Debt Instrument [Line Items]
Long-term debt		$ 50,000,000		0
Stated interest rate		3.20%	3.20%
Unsecured senior notes 3.54%
Debt Instrument [Line Items]
Long-term debt		$ 100,000,000		0
Stated interest rate		3.54%	3.54%
Variable Rate Debt
Debt Instrument [Line Items]
Long-term debt		$ 0		$ 0
Unsecured Private Placement, Debt Shell Facility
Debt Instrument [Line Items]
Number of debt instruments (in debt instruments) | debt_instrument		2
Debt Shelf Facility Prudential
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							$ 100,000,000	$ 75,000,000
Debt Shelf Facility Metlife
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000								$ 100,000,000
Debt instrument, issuance period	3 years