EMPLOYEE BENEFIT PLANS (Details) - Plan assets and benefit obligation of the defined benefit plans - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Change in benefit obligation:
Actuarial (gain) loss	$ 6,277
Change in plan assets:
Fair value of plan assets at beginning of fiscal year	145,610
Fair value of plan assets at end of fiscal year	147,145	$ 145,610
Pension Plan
Change in benefit obligation:
Benefit obligation at beginning of fiscal year	177,797	161,328
Interest cost	4,267	5,778	$ 5,084
Benefits paid	(10,747)	(10,790)
Actuarial (gain) loss	11,686	21,481
Benefit obligation at end of fiscal year	183,003	177,797	161,328
Change in plan assets:
Fair value of plan assets at beginning of fiscal year	145,610	150,680
Actual return on plan assets	4,261	2,606
Company contributions	8,021	3,114
Benefits paid	(10,747)	(10,790)
Fair value of plan assets at end of fiscal year	147,145	145,610	150,680
Projected benefit obligation in excess of plan assets	(35,858)	(32,187)
Amounts recognized in the statement of financial position consist of:
Accrued liabilities	0	0
Other liabilities (long-term)	(35,858)	(32,187)
Total Liabilities	(35,858)	(32,187)
Net actuarial losses	61,666	47,663
Prior service cost	0	0
Deferred taxes	(12,950)	(17,098)
Total Accumulated other comprehensive loss, net of tax	48,716	30,565
Net amount recognized at September 30,	12,858	(1,622)
Accumulated benefit obligations	183,003	177,797
Information for plans with accumulated benefit obligations in excess of plan assets:
ABO	183,003	177,797
PBO	183,003	177,797
Fair value of plan assets	147,145	145,610
Supplemental Employee Retirement Plan
Change in benefit obligation:
Benefit obligation at beginning of fiscal year	16,180	15,718
Interest cost	335	503	544
Benefits paid	(1,939)	(1,942)
Actuarial (gain) loss	1,494	1,901
Benefit obligation at end of fiscal year	16,070	16,180	15,718
Change in plan assets:
Fair value of plan assets at beginning of fiscal year	0	0
Actual return on plan assets	0	0
Company contributions	1,939	1,942
Benefits paid	(1,939)	(1,942)
Fair value of plan assets at end of fiscal year	0	0	$ 0
Projected benefit obligation in excess of plan assets	(16,070)	(16,180)
Amounts recognized in the statement of financial position consist of:
Accrued liabilities	(1,891)	(1,906)
Other liabilities (long-term)	(14,179)	(14,279)
Total Liabilities	(16,070)	(16,185)
Net actuarial losses	7,700	6,609
Prior service cost	0	14
Deferred taxes	(1,617)	(2,374)
Total Accumulated other comprehensive loss, net of tax	6,083	4,249
Net amount recognized at September 30,	(9,987)	(11,936)
Accumulated benefit obligations	16,070	16,180
Information for plans with accumulated benefit obligations in excess of plan assets:
ABO	16,070	16,180
PBO	16,070	16,180
Fair value of plan assets	$ 0	$ 0