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REGULATION - REGULATORY FILINGS (Details) $ in Thousands |  |  |  |  |  |  | 1 Months Ended | 4 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2018 USD ($) | Sep. 17, 2018 USD ($) | May 22, 2018 USD ($) | Mar. 01, 2018 USD ($) | Jul. 20, 2017 USD ($) | Oct. 01, 2016 USD ($) | Mar. 31, 2018 USD ($) | Sep. 30, 2017 USD ($) | Oct. 31, 2016 USD ($) | Sep. 30, 2016 USD ($) | Feb. 28, 2017 USD ($) | Sep. 30, 2018 USD ($) project
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets-noncurrent | $ 368,592 |  |  |  |  |  |  | $ 375,919 |  |  |  | $ 368,592
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  |  | 6.90%
Return on equity |  |  |  |  |  |  |  |  |  | 9.75% |  |
Environmental Remediation Costs |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 7 years
Postemployment and Other Benefit Costs |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 7 years
Deferred Storm Damage Costs |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 7 years
Other Regulatory Asset Noncurrent, PIM |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 7 years
Regulatory assets-noncurrent | 3,200 |  |  |  |  |  |  |  |  |  |  | $ 3,200
SAVEGREEN |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capital investments approved by the BPU | 354,300 | $ 135,000 |  |  |  |  |  |  |  |  |  |
Grants, rebates and loans provided to customers |  |  |  |  |  |  |  |  |  |  |  | 162,000
Increase in regulatory funding obligations |  |  |  |  |  |  |  |  |  |  |  | $ 16,100
SAVEGREEN | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 2 years
Program recovery term |  |  |  |  |  |  |  |  |  |  |  | 3 years
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  |  | 6.69%
Return on equity |  |  |  |  |  |  |  |  |  |  |  | 9.75%
SAVEGREEN | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Regulatory assets, amortization period |  |  |  |  |  |  |  |  |  |  |  | 10 years
Program recovery term |  |  |  |  |  |  |  |  |  |  |  | 10 years
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  |  | 7.76%
Return on equity |  |  |  |  |  |  |  |  |  |  |  | 10.30%
Energy Efficiency EE |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount | $ (8,800) |  |  |  |  |  |  |  |  |  |  |
March 2018 BGSS/CIP Filing |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  | $ 19,700 |  |  |  |  |  |  |  |
Requested customer refunds |  |  |  | $ 31,000 |  |  |  |  |  |  |  |
Approved customer refunds |  |  | $ 31,000 |  |  |  |  |  |  |  |  |
June 2016 BGSS/CIP Filing |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Customer bill credits |  |  |  |  |  |  |  |  |  |  | $ 42,000 |
June 2016 BGSS/CIP Filing | Conservation Incentive Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  | $ 43,900 |  |
June 2016 BGSS/CIP Filing | Basic Gas Supply Service |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  |  |  |  | $ (22,600) |  |
June 2017 BGSS/CIP Filing | Conservation Incentive Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  |  |  |  |  |  | $ (16,200) |  |  |  |  |
Increase in annual revenues |  |  |  |  |  |  | $ 3,700 |  |  |  |  |
May 2018 BGSS/CIP Filing | Conservation Incentive Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Increase in annual revenues |  | 10,300 |  |  |  |  |  |  |  |  |  |
Requested base rate increase, amount |  | (30,900) |  |  |  |  |  |  |  |  |  |
USF |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | 1,000 |  |  |  |  |  | (2,600) |  |  |  |
RAC |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | 1,400 |  |  |  |  |  | (2,400) |  |  |  |
NJCEP |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | 1,900 |  |  |  |  |  | $ 1,800 |  |  |  |
SAFE Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capital investments approved by the BPU |  |  |  |  |  |  |  |  | $ 200,000 |  |  | $ 130,000
Capital investments approved by the BPU, period |  |  |  |  |  |  |  |  |  |  |  | 4 years
Capital investments to be recovered approved by the Board of Public Utilities |  |  |  |  |  |  |  |  | $ 157,500 |  |  |
NJ RISE Program |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Program recovery term |  |  |  |  |  |  |  |  |  |  |  | 5 years
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  |  | 6.74%
Return on equity |  |  |  |  |  |  |  |  |  |  |  | 9.75%
Number of capital investment projects | project |  |  |  |  |  |  |  |  |  |  |  | 6
Originally filed petition for capital investments to Board of Public Utilities |  |  |  |  |  |  |  |  |  |  |  | $ 102,500
SAFE II and NJ RISE |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease), amount |  | $ 6,800 |  |  | $ 4,100 |  |  |  |  |  |  |
Public utilities, approved equity capital structure, percentage |  |  |  |  |  |  |  |  |  |  |  | 6.90%
SRL-Southern Reliability Link | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated cost of the SRL |  |  |  |  |  |  |  |  |  |  |  | $ 180,000
SRL-Southern Reliability Link | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated cost of the SRL |  |  |  |  |  |  |  |  |  |  |  | $ 215,000
LNG-Liquefied Natural Gas |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Capital investments to be recovered approved by the Board of Public Utilities |  |  |  |  |  | $ 36,500 |  |  |  |  |  |

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