- 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

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- 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

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Number of Solar Renewable Energy Certificates

+ References

No definition available.

+ Details

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Namespace Prefix:	njr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- 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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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- Details

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DERIVATIVE INSTRUMENTS - VOLUME (Details) certificate in Thousands	Mar. 31, 2018 USD ($) Bcf certificate	Sep. 30, 2017 Bcf	Jun. 01, 2015 USD ($)
Derivative [Line Items]
Derivative, notional amount \| $			$ 125,000,000
Foreign currency contracts
Derivative [Line Items]
Derivative, notional amount \| $	$ 8,800,000
Natural Gas Distribution \| Long \| Futures
Derivative [Line Items]
Outsanding long (short) derivatives, Volume	24.9	18.2
Natural Gas Distribution \| Long \| Physical
Derivative [Line Items]
Outsanding long (short) derivatives, Volume	33.2	32.1
Energy Services \| Physical commodity contracts
Derivative [Line Items]
Number of SRECs \| certificate	567
Energy Services \| Short \| Futures
Derivative [Line Items]
Outsanding long (short) derivatives, Volume	(13.0)	(16.4)
Energy Services \| Short \| Physical
Derivative [Line Items]
Outsanding long (short) derivatives, Volume	36.5	(13.1)