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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Jun. 30, 2018 | Dec. 31, 2019 | Jun. 30, 2019 | Jun. 30, 2018
Pension and other postretirement benefit plans |  |  |  |  |  |  |
Pension settlement expense |  |  |  |  |  | $ 1,634 | $ 1,085
Pension settlement expense, net of tax |  | $ 206 |  | $ 320 |  | 1,213 | 806
Nonunion Defined Benefit Pension Plan |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |
Pension settlement expense |  | 278 |  | 431 |  | 1,634 | 1,085
Pension settlement expense, net of tax |  | 200 |  | 300 |  | 1,200 | 800
Lump-sum distributions |  | $ 3,000 |  | $ 3,700 |  | $ 17,900 | $ 8,500
Expected return on plan assets (as a percent) |  | 0.00% | 1.40% |  |  |  |
Nonunion Defined Benefit Pension Plan | Forecast |  |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |  |
Pension settlement expense |  |  |  |  | $ 2,000 |  |
Pension settlement expense, net of tax |  |  |  |  | 1,500 |  |
Employer contributions |  |  |  |  | $ 7,000 |  |
Expected return on plan assets (as a percent) | 0.00% |  |  |  |  |  |

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