INCOME TAXES - Schedule of deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Deferred tax assets:
Bad debt reserves	$ 2,066	$ 3,980
Inventory reserves	11,298	9,371
Deferred compensation (equity compensation and defined benefit plans)	10,598	18,904
Compensation benefits	5,269	5,499
Insurance reserve	2,183	1,918
Warranty reserve	3,761	3,981
Lease liabilities	39,378	43,045
Net operating loss	10,706	9,618
Tax credits	7,198	7,031
Capital loss carryback	2,533	2,205
Other reserves and accruals	7,474	6,094
Deferred tax assets, gross	102,464	111,646
Valuation allowance	(10,425)	(9,824)
Total deferred tax assets	92,039	101,822
Deferred tax liabilities:
Goodwill and intangibles	(46,585)	(44,051)
Property, plant and equipment	(53,817)	(48,172)
Right-of-use assets	(38,511)	(41,747)
Other	(1,232)	(634)
Total deferred tax liabilities	(140,145)	(134,604)
Net deferred tax liabilities	$ (48,106)	$ (32,782)