INCOME TAXES - ADDITIONAL INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2023	Sep. 30, 2024
Income Tax Contingency [Line Items]
ITC carryforward	$ 149,700		$ 191,600
Effective term	20 years
Potential net capital loss	$ 56,600
Reversal of a valuation allowance for certain deferred tax assets		$ 15,800
Operating loss carryforward, valuation allowance	400
Unrecognized tax benefits	4,993	$ 4,978	4,993
Capital Loss Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, valuation allowance	5,100		5,100
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 476,100		$ 634,700
State and Local Jurisdiction | Minimum
Income Tax Contingency [Line Items]
Effective term	7 years
State and Local Jurisdiction | Maximum
Income Tax Contingency [Line Items]
Effective term	20 years