DERIVATIVE INSTRUMENTS - BROKER MARGIN DEPOSITS (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016
NJNG
Derivative [Line Items]
Broker margin - Current assets	$ 4,178	$ 4,822
NJRES
Derivative [Line Items]
Broker margin - Current assets	$ 15,965	$ 42,822

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.

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