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NATURE OF THE BUSINESS (Details) | 3 Months Ended
--- | ---
Dec. 31, 2013 Customers
Steckman Ridge [Member] |
Equity method investment, ownership percentage | 50.00%
Iroquois [Member] |
Equity method investment, ownership percentage | 5.53%
NJNG [Member] |
Total retail customers | 501,600

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- Definition Total number of retail customers specific to NJNG + References No definition available. + Details
Name: | njr_TotalRetailCustomers
Namespace Prefix: | njr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant