REVENUE - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Percentage of performance obligations recognized at a point in time	86.00%
Percentage of performance obligations recognized over time	14.00%
Favorable (unfavorable) catch-up adjustments to income from operations	$ (10,650)	$ (4,500)	$ 1,400
Accumulated estimated costs to complete loss contracts	10,800
Contract assets, net of progress payments	84,426	105,111
Decrease in contract assets balance	(20,685)
Contract assets, before allowance for credit Loss, noncurrent	7,500	13,100
Billings in excess of costs	24,386	$ 26,259
Increase (decrease) in contract liability	$ (1,873)
Minimum | Construction and Professional Products and Home and Building Products Segments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment term	15 days
Maximum | Construction and Professional Products and Home and Building Products Segments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Payment term	90 days