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PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Nonunion) (Details) $ in Thousands | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Sep. 30, 2019 USD ($) plan person | Mar. 31, 2019 | Sep. 30, 2018 USD ($) | Sep. 30, 2019 | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($)
Pension and other postretirement benefit plans |  |  |  |  |  |
Pension settlement expense |  |  |  |  | $ 8,135 | $ 1,603
Pension settlement expense, net of tax | $ 5,850 |  | $ 384 |  | 7,063 | 1,190
Noncash charge to pension settlement expense | $ 4,000 |  |  |  | 4,000 |
Nonunion Defined Benefit Pension Plan |  |  |  |  |  |
Pension and other postretirement benefit plans |  |  |  |  |  |
Number of plan participants for which vested pension benefits were settled | person | 120 |  |  |  |  |
Number of plan participants for which benefit obligation was transferred to PBGC. | plan | 30 |  |  |  |  |
Pension settlement expense | $ 2,530 |  | 518 |  | 4,164 | 1,603
Pension settlement expense, net of tax | 1,900 |  | 400 |  | 3,100 | 1,200
Lump-sum distributions | 16,000 |  | $ 3,100 |  | 33,900 | $ 11,600
Nonparticipating annuity contract purchase price | 14,000 |  |  |  |  |
Payment to purchase annuity contract | 14,000 |  |  |  |  |
Transfer of remaining obligation to PGBC | 1,500 |  |  |  |  |
Noncash charge to pension settlement expense | 4,000 |  |  |  | 4,000 |
Employer contributions | $ 7,700 |  |  |  | $ 7,710 |
Expected return on plan assets (as a percent) |  | 1.40% |  | 0.00% |  |

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