DEBT, NJR SHORT-TERM DEBT (Details) - NJR		Sep. 30, 2016 USD ($) debt_instrument	Sep. 30, 2015 USD ($)
Letters of credit
Short-term Debt [Line Items]
Number of debt instruments (in debt instruments) | debt_instrument		7
Letters of credit outstanding, amount		$ 14,400,000	$ 16,500,000
Letters of Credit on Behalf of NJRES
Short-term Debt [Line Items]
Number of debt instruments (in debt instruments) | debt_instrument		2
Letters of credit outstanding, amount		$ 9,100,000
Letters of Credit on Behalf of NJRCEV
Short-term Debt [Line Items]
Number of debt instruments (in debt instruments) | debt_instrument		5
Letters of credit outstanding, amount		$ 5,300,000
Committed Credit Facilities Due September 2020 | Bank revolving credit facilities
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	[1]	425,000,000	425,000,000
Bank revolving credit facilities
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity, incremental increase		5,000,000
Line of credit facility, maximum borrowing capacity, maximum increase		100,000,000
Uncommitted Credit Facilities | Bank revolving credit facilities
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	[2]	$ 0	$ 100,000,000

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

[2] Uncommitted credit facilities, which require no commitment fees.