EMPLOYEE BENEFIT PLANS - Weighted average assumptions (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Weighted average assumptions used for the pension calculations
Discount rate for net periodic benefit costs (as a percent)	3.79%	3.64%	4.27%
Discount rate for year-end obligations (as a percent)	4.27%	3.79%	3.64%
Expected return on plan assets (as a percent)	6.06%	6.17%	5.89%