INCOME TAXES - ADDITIONAL INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2020
Income Tax Contingency [Line Items]
Deferred employer portion of OASDI	$ 2,700	$ 5,100
ITC carryforward	$ 211,800	224,200
Effective term	20 years
Potential net capital loss	$ 56,600	61,800
Valuation allowance	22,241	23,613
Operating loss carryforward, valuation allowance	17,200	17,300
Investment tax credit, solar property, percentage			26.00%
Capital Loss Carryforward
Income Tax Contingency [Line Items]
Tax credit carryforward, valuation allowance	5,100	6,400
State and Local Jurisdiction
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 544,400	$ 554,600
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