DERIVATIVE INSTRUMENTS, BROKER MARGIN DEPOSITS (Details) (USD $) In Thousands	Jun. 30, 2011	Sep. 30, 2010
Restricted broker margin accounts	$ 27,326	$ 19,241
Restricted broker margin accounts	0	28,459
NJNG [Member]
Restricted broker margin accounts	13,034	19,241
NJRES [Member]
Restricted broker margin accounts	14,292
Restricted broker margin accounts		$ (28,459)

The amount due to the entity from other broker-dealers in the form of a deposit paid by the counterparty to demonstrate an intention to complete a purchase (good faith deposit) and also the amount due in the form of collateral deposited by the counterparty to cover the credit risk assumed by the entity (margin deposit).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 4
-Paragraph 24
-IssueDate 2006-05-01
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant