RESTRUCTURING CHARGES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended			12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 150	$ 2,472		$ 273	$ 3,619
Employee-Related
Restructuring Cost and Reserve [Line Items]
Restructuring charges					1,700	$ 5,100
One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges					200
VSP
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 17,300		$ 100	$ 2,300
Forecast | One-time Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 300