EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018
EMPLOYEE BENEFIT PLANS (Details) [Line Items]
Defined contribution plan, employer discretionary contribution amount		$ 11,788	$ 11,053	$ 10,079
Postemployment benefits liability		1,852	1,699
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		$ 3,148	3,649	1,993
Change in discount rate		10.00%
Tax benefit for amortization of pension cost		$ 221	342	1,170
Defined benefit plan, actuarial gain (loss)		4,167
Service cost		$ 14
Adjusted funding target attainment percent					91.30%
Adjusted funding target attainment percent, threshold					80.00%
Defined benefit plan, target plan asset allocations		100.00%
Defined benefit plans, estimated future employer contributions in next fiscal year		$ 2,440
Completion period of service		1 year
Maximum compensation of proportion		$ 280
Employee stock ownership plan (ESOP), compensation expense		2,630	9,532	5,643
Special Dividend ESOP Charges	$ 2,125		2,588
Employee stock ownership plan (ESOP), deferred shares, fair value		47,378	40,010
Other Postretirement Benefits Plan [Member]
EMPLOYEE BENEFIT PLANS (Details) [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax		(146)	(60)
Pension and other postretirement benefit expense		50	45
Supplemental Employee Retirement Plan [Member]
EMPLOYEE BENEFIT PLANS (Details) [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax		(4,249)	(3,396)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		775	1,186	2,077
Company contributions		1,942	3,001
Defined benefit plan, actuarial gain (loss)		(1,901)	14,452
Defined benefit plan, expected future benefit payments, next twelve months		1,900
Pension Plan [Member]
EMPLOYEE BENEFIT PLANS (Details) [Line Items]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans, net of tax		(30,565)	(12,985)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)		(3,923)	(4,897)	$ (4,070)
Company contributions		3,114	2,449
Defined benefit plan, actuarial gain (loss)		(21,481)	$ 7,562
Defined benefit plan, expected future benefit payments, next twelve months		11,017
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year		$ 6,758