INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Operating Loss Carryforwards [Line Items]
Tax rate reconciliation, disallowed loss on sale of business	$ 4,219
Tax rate reconciliation, disallowed goodwill impairment	3,001
Tax benefit of nontaxable solar manufacturing credits	12,258	$ 18,972
State income tax expense		12,805	$ 21,630
Tax rate reconciliation, tax benefit from share-based compensation		13,773
Tax rate reconciliation, solar tax credits			39,493
Unrecognized tax benefits	4,517	3,367	2,581	$ 985
Accrued interest and penalties	648	516
Unrecognized tax benefits, increase (decrease)	1,332	1,370	1,792
Increase (decrease) of unrecognized tax benefits related to various state jurisdictions' uncertain tax positions	(182)	(585)	(196)
Increase (decrease) of accrued penalties and interest for uncertain tax positions	132	$ 281	$ 158
Undistributed income	182,176
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carrying forwards	24,687
Non-U.S.
Operating Loss Carryforwards [Line Items]
Operating loss carrying forwards	$ 73,879
Operating loss carryforwards expiration term (year)	5 years