REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	$ 36,842us-gaap_RegulatoryAssetsCurrent	$ 26,862us-gaap_RegulatoryAssetsCurrent
Regulatory assets-noncurrent	369,176us-gaap_RegulatoryAssetsNoncurrent	377,575us-gaap_RegulatoryAssetsNoncurrent
Regulatory liability-current	0us-gaap_RegulatoryLiabilityCurrent	6,072us-gaap_RegulatoryLiabilityCurrent
Regulatory liabilities-noncurrent	65,328us-gaap_RegulatoryLiabilityNoncurrent	61,326us-gaap_RegulatoryLiabilityNoncurrent
Derivatives at Fair Value, Net [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability-current	0	320
Conservation Incentive Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability-current	0	5,752
Cost of Removal Obligation [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	58,723	61,163
Derivatives Net, Noncurrent [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	0	57
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	6,605	106
New Jersey Clean Energy Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	13,166	14,285
Derivatives at Fair Value, Net [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	18,866	0
Conservation Incentive Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	1,556	0
Underrecovered Gas Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	3,254	12,577
Environmental Remediation Costs Expended, Net of Recoveries [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	26,226	30,916
Environmental Remediation Costs Liability for Future Expenditures [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	177,000	177,000
Deferred Income Taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	9,968	9,968
SAVEGREEN [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	28,411	29,180
Postemployment and Other Benefit Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	106,503	108,507
Deferred Superstorm Sandy Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	15,207	15,207
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	$ 5,861	$ 6,797

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

+ Details

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- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 405

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

+ Details

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- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ 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 210.5-02.24)

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

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