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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) $ in Thousands | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2018 USD ($) | Mar. 31, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Mar. 31, 2017 USD ($) person | Mar. 31, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($)
Pension and other postretirement benefit plans |  |  |  |  |  |  |  |
Pension settlement expense, pre-tax |  |  |  |  |  |  | $ 1,603 | $ 3,644
Pension settlement expense, net of tax |  |  | $ 384 | $ 577 |  |  | 1,190 | 2,227
Nonunion Defined Benefit Pension Plan |  |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |  |
Pension settlement expense, pre-tax |  |  | 518 | 943 |  |  | 1,603 | 3,644
Pension settlement expense, net of tax |  |  | 400 | 600 |  |  | 1,200 | 2,200
Lump-sum distributions |  |  | $ 3,100 | $ 5,800 |  |  | 11,600 | $ 23,100
Premium paid to purchase nonparticipating annuity contract |  |  |  |  | $ 7,600 |  |  |
Number of plan participants for which vested pension benefits were settled | person |  |  |  |  | 50 |  |  |
Employer contributions | $ 5,500 |  |  |  |  |  | $ 5,500 |
Nonunion Defined Benefit Pension Plan | Forecast |  |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |  |
Employer contributions |  | $ 13,000 |  |  |  |  |  |
Nonunion Defined Benefit Pension Plan | Minimum | Forecast |  |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |  |
Pension settlement expense, pre-tax |  |  |  |  |  | $ 15,000 |  |
Nonunion Defined Benefit Pension Plan | Maximum | Forecast |  |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |  |
Pension settlement expense, pre-tax |  |  |  |  |  | $ 21,000 |  |

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