REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012
Regulatory Assets And Liabilities [Line Items]
Regulatory assets current	$ 31,194	$ 32,734
Regulatory assets noncurrent	457,880	441,263
Regulatory liability current	0	1,169
Regulatory liability noncurrent	66,743	67,077
Derivatives, net, current [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability current	0	1,169
Cost of removal obligation [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability noncurrent	65,382	65,994
Derivatives net, noncurrent [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability noncurrent	966	1,000
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory liability noncurrent	395	83
Conservation Incentive Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets current	25,681	25,681
Underrecovered gas costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets current	5,513	7,053
Environmental remediation costs expended, net of recoveries [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	56,333	59,745
Environmental remediation costs liability for future expenditures [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	182,000	182,000
Deferred income and other taxes [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	11,405	11,405
Energy Efficiency Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	28,762	26,025
New Jersey Clean Energy Program [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	13,621	5,619
Postemployment and other benefit costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	140,098	142,495
Deferred Superstorm Storm Costs [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	14,110	0
Other [Member]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets noncurrent	$ 11,551	$ 13,974

- Definition

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.

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