DERIVATIVE INSTRUMENTS - BROKER MARGIN DEPOSITS (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Natural Gas Distribution
Derivative [Line Items]
Broker margin - Current assets	$ 1,845	$ 2,661
Energy Services
Derivative [Line Items]
Broker margin - Current assets	$ 51,296	$ 23,166

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