Public Utilities And Other Property, Plant and Equipment, Gross

No definition available.

Name:	njr_PublicUtilitiesAndOtherPropertyPlantandEquipmentGross
Namespace Prefix:	njr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Public Utilities And Other Property, Plant and Equipment, Net

+ References

No definition available.

+ Details

Name:	njr_PublicUtilitiesAndOtherPropertyPlantandEquipmentNet
Namespace Prefix:	njr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.14)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.13)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_RegulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_GasDistributionMember
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:	us-gaap_PublicUtilityAxis=us-gaap_GasTransmissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=njr_StorageFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_UnregulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=njr_SolarPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=njr_MidstreamPropertyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_PropertyPlantAndEquipmentOtherTypesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PROPERTY PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands		12 Months Ended
	Jul. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property Classifications
Total property, plant and equipment		$ 4,464,966	$ 3,501,407
Accumulated depreciation and amortization		(742,197)	(691,774)
Property, plant and equipment, net		3,722,769	2,809,633
Utility \| Distribution facilities
Property Classifications
Total property, plant and equipment		$ 2,688,885	2,419,381
Utility \| Distribution facilities \| Minimum
Property Classifications
Estimated Useful Lives		38 years
Utility \| Distribution facilities \| Maximum
Property Classifications
Estimated Useful Lives		74 years
Utility \| Transmission facilities
Property Classifications
Total property, plant and equipment		$ 332,947	330,912
Utility \| Transmission facilities \| Minimum
Property Classifications
Estimated Useful Lives		35 years
Utility \| Transmission facilities \| Maximum
Property Classifications
Estimated Useful Lives		56 years
Utility \| Storage facilities
Property Classifications
Total property, plant and equipment		$ 79,922	79,916
Utility \| Storage facilities \| Minimum
Property Classifications
Estimated Useful Lives		34 years
Utility \| Storage facilities \| Maximum
Property Classifications
Estimated Useful Lives		47 years
Nonutility \| Solar property
Property Classifications
Total property, plant and equipment		$ 674,930	$ 593,867
Nonutility \| Solar property \| Minimum
Property Classifications
Estimated Useful Lives	15 years	15 years	15 years	15 years
Nonutility \| Solar property \| Maximum
Property Classifications
Estimated Useful Lives	35 years	35 years	25 years	25 years
Nonutility \| Storage and transportation property
Property Classifications
Total property, plant and equipment		$ 428,491	$ 28,445
Nonutility \| Storage and transportation property \| Minimum
Property Classifications
Estimated Useful Lives		5 years
Nonutility \| Storage and transportation property \| Maximum
Property Classifications
Estimated Useful Lives		50 years
Nonutility \| All other property
Property Classifications
Total property, plant and equipment		$ 259,791	$ 48,886
Nonutility \| All other property \| Minimum
Property Classifications
Estimated Useful Lives		5 years
Nonutility \| All other property \| Maximum
Property Classifications
Estimated Useful Lives		35 years