EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2020	Jan. 01, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, employer discretionary contribution amount	$ 11,956	$ 11,788	$ 11,053
Postemployment benefits liability	1,833	1,852
Non-service cost components of net periodic benefit cost (credit)	$ (1,559)	(3,148)	(3,649)
Change in discount rate	10.00%
Tax benefit for amortization of pension cost	$ 878	221	342
Defined benefit plan, actuarial gain (loss)	(6,277)
Service cost	15
Adjusted funding target attainment percent				93.70%
Adjusted funding target attainment percent, threshold					80.00%
Defined benefit plans, estimated future employer contributions in next fiscal year	$ 2,107
Completion period of service	1 year
Maximum compensation of proportion	$ 285
Employee stock ownership plan (ESOP), compensation expense	2,878	2,629	9,532
Special dividend ESOP charges			$ 2,588
Employee stock ownership plan (ESOP), deferred shares, fair value	40,217	47,378
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax	(196)	(146)
Pension and other postretirement benefit expense	46	50
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax	(6,083)	(4,249)
Defined benefit plan, actuarial gain (loss)	(1,494)	(1,901)
Defined benefit plan, expected future benefit payments, next twelve months	1,891
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax	(48,716)	(30,565)
Defined benefit plan, actuarial gain (loss)	(11,686)	$ (21,481)
Defined benefit plan, expected future benefit payments, next twelve months	11,006
Defined benefit plan, expected future employer contributions, current fiscal year	$ 2,764