EMPLOYEE BENEFIT PLANS - Pension benefit obligations and fair value of plan assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
EMPLOYEE BENEFIT PLANS
Accumulated Benefit Obligation	$ 106,205	$ 109,976
Changes in projected benefit obligations
Projected benefit obligation at beginning of year	109,976	109,731
Interest cost	4,077	4,053	$ 4,266
Actuarial (gain) loss	(2,143)	3,633
Benefits paid	(5,705)	(7,441)
Projected benefit obligation at end of year	106,205	109,976	109,731
Change in plan assets
Fair value of plan assets at beginning of year	92,816	90,748
Actual return on plan assets	7,754	9,470
Employer contribution	32	39
Benefits paid	(5,705)	(7,441)
Fair value of plan assets at end of year	94,897	92,816	$ 90,748
Funded status of the plan at end of year	(11,308)	$ (17,160)
Net actuarial loss, which is expected to be amortized in next year's periodic benefit cost	$ 1,200