XML 66 R51.htm IDEA: XBRL DOCUMENT
v3.10.0.1

DERIVATIVE INSTRUMENTS - VOLUME (Details) certificate in Thousands, $ in Millions | Jun. 30, 2018 USD ($) Bcf certificate | Sep. 30, 2017 Bcf
--- | --- | ---
Foreign currency contracts |  |
Derivative [Line Items] |  |
Derivative, notional amount | $ | $ 7.9 |
Natural Gas Distribution | Long | Futures |  |
Derivative [Line Items] |  |
Outsanding long (short) derivatives, Volume | 25.8 | 18.2
Natural Gas Distribution | Long | Physical |  |
Derivative [Line Items] |  |
Outsanding long (short) derivatives, Volume | 31.6 | 32.1
Energy Services | Physical commodity contracts |  |
Derivative [Line Items] |  |
Number of SRECs | certificate | 702 |
Energy Services | Short | Futures |  |
Derivative [Line Items] |  |
Outsanding long (short) derivatives, Volume | (30.2) | (16.4)
Energy Services | Short | Physical |  |
Derivative [Line Items] |  |
Outsanding long (short) derivatives, Volume | 19.9 | (13.1)

X
- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Solar Renewable Energy Certificates + References No definition available. + Details
Name: | njr_NumberofSolarRenewableEnergyCertificates
Namespace Prefix: | njr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=njr_NaturalGasDistributionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_LongMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_FutureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=njr_EnergyServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EnergyRelatedDerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PositionAxis=us-gaap_ShortMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |