Line of Credit Facility, Issuance period

No definition available.

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

- Definition

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

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The cash inflow from amounts received from a long-term debt instrument secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfFirstMortgageBond
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow from the repayment of a long-term debt instrument issued, secured by a first mortgage deed of trust, containing a pledge of real property. The lender has the highest claim on the property in case of default.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_RepaymentsOfFirstMortgageBond
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

+ Details

Name:	us-gaap_RepaymentsOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The gross proceeds received from the asset(s) sold in connection with the transaction involving the sale of property to another party and the lease back to the seller.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 51

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51840-112757

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 52

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51843-112757

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 40

-Section 55

-Paragraph 50

-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51831-112757

+ Details

Name:	us-gaap_SaleLeasebackTransactionGrossProceeds
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

DEBT - SCHEDULE OF LONG TERM DEBT (Details) (USD $)	6 Months Ended		24 Months Ended				6 Months Ended		6 Months Ended	3 Months Ended		1 Months Ended		1 Months Ended	6 Months Ended		0 Months Ended
DEBT - SCHEDULE OF LONG TERM DEBT (Details) (USD $)	Mar. 31, 2014	Mar. 31, 2013	May 10, 2013 NJR [Member] Debt Shelf Facility Metlife [Member]	Mar. 31, 2013 NJR [Member] Debt Shelf Facility Metlife [Member]	Mar. 31, 2014 NJR [Member] Debt Shelf Facility Metlife [Member] Unsecured Senior Note 1.94% [Member]	Mar. 31, 2014 NJR [Member] Debt Shelf Facility Metlife [Member] Unsecured Senior Note 2.51% [Member]	Mar. 31, 2014 NJR [Member] Debt Shelf Facility Prudential [Member]	Mar. 31, 2014 NJR [Member] Debt Shelf Facility Prudential [Member] Unsecured Senior Note 3.25% [Member]	Mar. 31, 2014 NJR [Member] Debt Shelf Facility Metlife 2 [Member]	Dec. 31, 2013 NJNG [Member]	Dec. 31, 2012 NJNG [Member]	Mar. 31, 2014 NJNG [Member] First Mortgage [Member] Series QQ [Member]	Mar. 31, 2014 NJNG [Member] First Mortgage [Member] Series HH [Member]	Mar. 31, 2014 NJNG [Member] First Mortgage [Member] Series RR [Member]	Mar. 31, 2014 NJNG [Member] Unsecured Debt [Member]	Mar. 14, 2014 NJNG [Member] Unsecured Debt [Member]	Apr. 10, 2014 Long-term Debt [Member] NJNG [Member] First Mortgage [Member] Series HH [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 100,000,000			$ 75,000,000		$ 100,000,000
Line of credit facility, issuance period			2 years				3 years		3 years
Amount issued and outstanding					25,000,000	25,000,000		50,000,000
Interest rate, stated percentage					1.94%	2.51%		3.25%				3.58%	5.00%	4.61%		4.77%
Repayments of First Mortgage Bond																	12,000,000
Repayments of Long-term Debt	65,017,000	3,833,000													60,000,000
Line of credit facility, remaining borrowing capacity									100,000,000
Proceeds from issuance of long-term debt												70,000,000		55,000,000
Sale leaseback transaction, gross proceeds										$ 7,600,000	$ 7,100,000