EMPLOYEE BENEFIT PLANS - Pension and post-retirement plan assets by asset category (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 144,091	$ 160,523
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	141,012	160,238
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	94,471	121,655
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	37,057	27,297
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	9,484	11,286	$ 9,362
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	9,484	11,286
Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	6,178	1,867
Cash and equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	6,178	1,867
Cash and equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Cash and equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Government agency securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	28,635	36,825
Government agency securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	25,932	32,217
Government agency securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	2,703	4,608
Government agency securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Debt instruments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	4,930	3,769
Debt instruments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	1,326	1,063
Debt instruments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	3,604	2,706
Debt instruments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	59,190	84,129
Equity securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	59,190	84,129
Equity securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Equity securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	17,572	11,286
Commingled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Commingled funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	8,088	0
Commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	9,484	11,286
Limited partnerships and hedge fund investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	22,662	19,823
Limited partnerships and hedge fund investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Limited partnerships and hedge fund investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	22,662	19,823
Limited partnerships and hedge fund investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Other Securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	1,845	2,539
Other Securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	1,845	2,379
Other Securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	160
Other Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	0	0
Accrued income and plan receivables
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	265	$ 285
Fully benefit-responsive investment contract
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 2,814