FINANCIAL INSTRUMENTS (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Mar. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted investments held In escrow		$ 1,700,000sji_RestrictedInvestmentsHeldInEscrow	$ 1,700,000sji_RestrictedInvestmentsHeldInEscrow
Margin accounts with selected counterparties to support risk management activities		58,900,000us-gaap_MarginDepositAssets	63,700,000us-gaap_MarginDepositAssets
Investment in Affiliates		67,754,000us-gaap_EquityMethodInvestments	68,351,000us-gaap_EquityMethodInvestments
Notes Receivable - Affiliate		36,525,000	36,799,000
South Jersey Gas Company \| Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term receivables, net of unamortized discount		14,900,000	15,000,000
Imputed interest on long term receivables		1,200,000	1,300,000
Energenic US LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest (in hundredths)		50.00%
Contract term (in years)	20 years
Investment in Affiliates		15,100,000
Notes Receivable - Affiliate		$ 13,900,000

Contract Term

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- Definition

Unused proceeds on restricted investments that are required to be held in escrow. Includes interest earned.

+ References

No definition available.

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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)

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ 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 210.5-02.12)

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-SubTopic 10

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- Definition

The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

+ References

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- Definition

Amounts due from parties associated with the reporting entity as evidenced by a written promise to pay, due after 1 year (or 1 business cycle).

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

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-Topic 850

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-Name Regulation S-X (SX)

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-Publisher FASB

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-Glossary Related Parties

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- Definition

Disclosure of the unamortized amount of the discount on the note or receivable which is deducted from the face amount of the receivable or loan. The discount or premium is the difference between the present value and the face amount.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 1A

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The receivable or note face amount less the unamortized discount or premium.

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