REGULATORY MATTERS (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017
Regulated Operations [Abstract]
Remaining recovery period for certain regulatory assets for which no return on investment during recovery period is provided (in years)	20 years
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided (in years)		15 years