Annual report pursuant to Section 13 and 15(d)

PENSION AND OTHER POSTRETIREMENT PLANS - Weighted-Average Assumptions for Principal Retirement and Other Postretirement Benefit Plans (Details)

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PENSION AND OTHER POSTRETIREMENT PLANS - Weighted-Average Assumptions for Principal Retirement and Other Postretirement Benefit Plans (Details)
12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2016
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 4.21% 3.76% 3.51%
Return on plan assets 6.75% 6.75% 7.25%
Compensation increase 3.50% 3.50% 3.50%
Other Postretirement      
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 4.19% 3.72% 3.42%
Return on plan assets 0.00% 0.00% 0.00%
Compensation increase 0.00% 0.00% 0.00%