Agreement for Natural Gas Storage Capacity Between NJNG and NJR subsidaries

Name:	njr_AgreementForNaturalGasStorageCapacityBetweenNjngAndAffiliate
Namespace Prefix:	njr
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Demand fees incurred associated with contracts for storage and/or pipeline capacity and recognized as a component of gas purchases.

+ Details

Name:	njr_DemandFees
Namespace Prefix:	njr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Agreement between subsidiaries as a result of gas storage sold under asset management agreement

+ Details

Name:	njr_NaturalGasStorageSoldUnderAssetManagementAgreementFromNjngToNjres
Namespace Prefix:	njr
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Annual Projected Demand Fees based upon a related party agreement between various NJR Subsidiaries

+ Details

Name:	njr_ProjectedAnnualDemandFeesUnderRelatedPartyAgreement
Namespace Prefix:	njr
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of obligations due all related parties.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 17

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 2

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(k)(1))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph k

-Subparagraph 1

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 03

-Paragraph 15

-Subparagraph 3, 4

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.17)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(3),(4))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Expenses recognized during the period resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 2

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
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Period Type:	duration

RELATED PARTY TRANSACTIONS (Details) (USD $)	12 Months Ended
RELATED PARTY TRANSACTIONS (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Related Party Transaction [Line Items]
Demand Fees	$ 211,200,000	$ 203,700,000	$ 197,400,000
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand Fees Expense Recognized by NJRES Pertaining to Related Party Agreement	5,600,000
Due to Related Parties	237,000
NJRES to Iroquois Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties	389,000
NJNG to NJRES Affilate [Member]
Related Party Transaction [Line Items]
Natural Gas Sold at Cost Under Asset Management Agreement (MMcf)	1,000
NJNG to Steckman RIdge Affiliate
Related Party Transaction [Line Items]
Demand Fees Expense Recognized by NJRES Pertaining to Related Party Agreement	9,300,000
Agreement for Natural Gas Storage Capacity Between NJNG and Affiliate (MMcf)	3,000
Approximate Annual Demand Fees Under Agreement from April 1 2010 to March 31 2020	9,300,000
Due to Related Parties	$ 775,000