Net Proceeds from Sale Leaseback Transaction, Financing Activities

No definition available.

Name:	njr_NetProceedsfromSaleLeasebackTransactionFinancingActivities
Namespace Prefix:	njr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Payments For Sale Leaseback Transaction, Financing Activities

+ References

No definition available.

+ Details

Name:	njr_PaymentsForSaleLeasebackTransactionFinancingActivities
Namespace Prefix:	njr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Sale Leaseback Transaction, Net Proceeds, Financing Activities, Solar

+ References

No definition available.

+ Details

Name:	njr_SaleLeasebackTransactionNetProceedsFinancingActivitiesSolar
Namespace Prefix:	njr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Sale Leaseback Transaction, Term Of Lease

+ References

No definition available.

+ Details

Name:	njr_SaleLeasebackTransactionTermOfLease
Namespace Prefix:	njr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69C
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=njr_NjngMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=njr_FixedInterestRateMaturing2051Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=njr_FixedInterestRateMaturing2061Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=njr_CleanEnergyVenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=njr_NjngMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DEBT - LONG TERM DEBT (Details) - USD ($) $ in Thousands	3 Months Ended
DEBT - LONG TERM DEBT (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Oct. 28, 2021
Debt Instrument [Line Items]
Proceeds from sale leaseback transaction	$ 17,300	$ 0
Proceeds from sale leaseback transaction - solar	3,300	12,124
Senior Notes \| Natural Gas Distribution
Debt Instrument [Line Items]
Face amount			$ 100,000
Senior Notes \| Natural Gas Distribution \| Fixed Interest Rate Maturing 2051
Debt Instrument [Line Items]
Face amount			$ 50,000
Stated interest rate			2.97%
Senior Notes \| Natural Gas Distribution \| Fixed Interest Rate Maturing 2061
Debt Instrument [Line Items]
Face amount			$ 50,000
Stated interest rate			3.07%
Clean Energy Ventures
Debt Instrument [Line Items]
Proceeds from sale leaseback transaction - solar	$ 3,300	12,100
Clean Energy Ventures \| Minimum
Debt Instrument [Line Items]
Sale leaseback transaction lease term	5 years
Clean Energy Ventures \| Maximum
Debt Instrument [Line Items]
Sale leaseback transaction lease term	15 years
Natural Gas Distribution
Debt Instrument [Line Items]
Proceeds from sale leaseback transaction	$ 17,300	$ 0
Payments for sale leaseback transaction	$ 1,100