EMPLOYEE BENEFIT PLANS (Details) - Pension and post-retirement plan assets by asset category - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	$ 147,145	$ 145,610
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	142,179	145,319
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	105,929	105,700
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	26,888	30,843
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	9,362	8,776	$ 0
Defined benefit plan, fair value of plan assets, subtotal excluding accrued income and plan receivables	9,362	8,776
Cash and equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	600	2,791
Cash and equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	600	2,791
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	39,811	37,416
Government agency securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	33,675	28,297
Government agency securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	6,136	9,119
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	2,901	3,178
Debt instruments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	179	182
Debt instruments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	2,722	2,996
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	68,987	72,517
Equity securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	68,987	72,517
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	9,362	8,776
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	0	0
Commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	9,362	8,776
Limited partnerships and hedge fund investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	17,867	18,569
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	17,867	18,569
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	2,651	2,072
Other Securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	2,488	1,913
Other Securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	163	159
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	$ 4,966	$ 291