Name:	sji_InvestmentInAffiliateNetOfGuarantees
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Length of Pipeline

No definition available.

Name:	sji_LengthofPipeline
Namespace Prefix:	sji_
Data Type:	num:lengthItemType
Balance Type:	na
Period Type:	instant

The maximum exposure to loss (i.e. risk) to the reporting entity should the affiliates (the parties associated with the reporting entity) become unable to continue operations.

No definition available.

Name:	sji_MaximumExposureToLossOnAffiliates
Namespace Prefix:	sji_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of net investments in, and advances to unconsolidated affiliates reported by an equity method investment of the entity.

No definition available.

Name:	sji_NetAdvancestoUnconsolidatedAffiliates
Namespace Prefix:	sji_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amounts due from parties associated with the reporting entity as evidenced by a written promise to pay.

No definition available.

Name:	sji_NotesReceivableRelatedPartiesCurrentNoncurrent
Namespace Prefix:	sji_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	num:percentItemType
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Period Type:	instant

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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=66011266&loc=d3e33918-111571

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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.

No definition available.

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

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_EnergenicUsLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_MillenniumAccountServicesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_PotatoCreekLlcPotatoCreekMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_PennEastPipelineCompanyLLCPennEastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: