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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 |  |  |

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