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RELATED PARTY TRANSACTIONS (Details) $ in Thousands |  | 12 Months Ended
--- | --- | ---
Apr. 01, 2010 USD ($) Bcf | Sep. 30, 2017 USD ($) Bcf / d contract | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($)
Related Party Transaction [Line Items] |  |  |  |
Demand fees recognized pertaining to related party agreement |  | $ 8,340 | $ 8,351 | $ 7,657
Due to related parties |  | $ 1,152 | 1,150 |
Number of asset management agreements | contract |  | 4 |  |
NJNG to NJRES Affiliate |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Asset management agreement, period | 10 years |  |  |
NJNG to Steckman RIdge Affiliate |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Natural gas sold at cost under asset management agreement (in Bcf) | Bcf | 3 |  |  |
Approximate annual demand fees under agreement | $ 9,300 |  |  |
Demand fees recognized pertaining to related party agreement |  | $ 5,590 | 5,562 | 5,700
Due to related parties |  | 775 | 775 |
NJRES to Steckman Ridge Affiliate |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Demand fees recognized pertaining to related party agreement |  | 2,750 | 2,789 | $ 1,957
Due to related parties |  | $ 377 | $ 375 |
NJNG to PennEast Affiliate |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Transportation precedent agreement, period |  | 15 years |  |
Transportation capacity under precedent agreement from NJNG with PennEast (in Bcf per day) | Bcf / d |  | 0.18 |  |

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