COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2020
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase orders outstanding for equipment, parts and supplies		$ 2.7
HPIDC Employee Injury Lawsuit - January 2018
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Settlement amount	$ 21.0
HPIDC Employee Injury Lawsuit - October 2017
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss contingency accrual	$ 9.5