-- None. No documentation exists for this element. --

No definition available.

Name:	sji_AffiliationsAbstract
Namespace Prefix:	sji_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Due from Affiliate, Noncurrent, Secured By Property, Plant, And Equipment

+ References

No definition available.

+ Details

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

- Definition

Due from Affiliate, Noncurrent, Unsecured

+ References

No definition available.

+ Details

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

- Definition

Investments in parties associated with the reporting entity net of guarantees to be paid by the reporting entity (which are included as liabilities on the balance sheet).

+ References

No definition available.

+ Details

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

- Definition

Length of Pipeline

+ References

No definition available.

+ Details

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

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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

- Definition

Identify the stated interest rate per the agreement, for example, leasing and debt arrangements between related parties.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=114873854&loc=SL114874292-224272

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

+ Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_PotatoCreekLlcPotatoCreekMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_PennEastPipelineCompanyLLCPennEastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_MillenniumAccountServicesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_EnerConnexLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sji_SouthJerseyResourceGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_EnergyMarkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sji_MarinaEnergyLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=sji_EnergenicUsLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sji_SJIMidstreamLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sji_SouthJerseyEnergyCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

AFFILIATIONS, DISCONTINUED OPERATIONS AND RELATED-PARTY TRANSACTIONS - AFFILIATIONS (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) mi	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2017
Affiliations [Abstract]
Notes receivable from affiliate	$ 15.2	$ 18.2
Length of natural gas pipeline (in miles) \| mi	118
Net investments in unconsolidated affiliates	$ 6.6	32.1
Notes receivable secured by property, plant, and equipment of affiliates	$ 13.6
Interest accrual on secured notes receivable	7.50%
Unsecured notes receivable	$ 1.6
Net asset - included in investment in affiliates and other noncurrent liabilities	76.1
Combined equity contributions and the notes receivable - affiliate	$ 91.3
Potato Creek
Affiliations [Abstract]
Equity interest	30.00%
PennEast
Affiliations [Abstract]
Length of natural gas pipeline (in miles) \| mi	118
Millennium Account Services, LLC
Affiliations [Abstract]
Equity interest				50.00%
EnerConnex, LLC
Affiliations [Abstract]
Equity interest	25.00%
SJRG \| EnergyMark
Affiliations [Abstract]
Total Operating Revenues/Affiliates	$ 41.6	$ 37.5	$ 31.4
Marina Energy LLC \| Energenic
Affiliations [Abstract]
Equity interest	50.00%
Midstream \| PennEast
Affiliations [Abstract]
Equity interest	20.00%
South Jersey Energy Company \| EnergyMark
Affiliations [Abstract]
Equity interest	33.00%