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WORKERS' COMPENSATION AND PNEUMOCONIOSIS (Tables) | 9 Months Ended
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Sep. 30, 2020
Accrued Workers Compensation And Pneumoconiosis Benefits |
Reconciliation of changes in workers' compensation liability | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Three Months Ended | ​ | Nine Months Ended |
​ | ​ | September 30, | ​ | September 30, | ​
​ | ​ | 2020 |  | 2019 |  | 2020 |  | 2019 | ​
​ | ​ | (in thousands) | ​
Beginning balance | ​ | $ | 54,478 | ​ | $ | 53,425 | ​ | $ | 53,384 | ​ | $ | 49,539 | ​
Accruals increase | ​ |  | 1,599 | ​ |  | 2,395 | ​ |  | 3,539 | ​ |  | 6,603 | ​
Payments | ​ |  | (2,123) | ​ |  | (2,663) | ​ |  | (6,686) | ​ |  | (8,588) | ​
Interest accretion | ​ |  | 319 | ​ |  | 402 | ​ |  | 958 | ​ |  | 1,204 | ​
Valuation loss (1) | ​ |  | — | ​ |  | — | ​ |  | 3,078 | ​ |  | 4,801 | ​
Ending balance | ​ | $ | 54,273 | ​ | $ | 53,559 | ​ | $ | 54,273 | ​ | $ | 53,559 | ​
(1) | Our estimate of the liability for the present value of current workers′ compensation benefits is based on our actuarial calculations. Our actuarial calculations are based on a blend of actuarial projection methods and numerous assumptions including claims development patterns, mortality, medical costs and interest rates. We conducted a 2020 mid-year review of our actuarial assumptions which resulted in a valuation loss due to unfavorable changes in claims development and a decrease in the discount rate from 2.81% to 2.05%. Our 2019 mid-year actuarial review resulted in a valuation loss due to unfavorable changes in claims development and a decrease in the discount rate from 3.89% to 3.06%.
Pneumoconiosis benefits |
Accrued Workers Compensation And Pneumoconiosis Benefits |
Components of net periodic benefit cost |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Three Months Ended | ​ | Nine Months Ended | ​
​ | ​ | September 30, | ​ | September 30, | ​
​ | ​ | 2020 |  | 2019 |  | 2020 |  | 2019 |
​ | ​ | (in thousands) | ​
Service cost | ​ | $ | 882 | ​ | $ | 656 | ​ | $ | 2,643 | ​ | $ | 1,947 |
Interest cost (1) | ​ |  | 750 | ​ |  | 761 | ​ |  | 2,249 | ​ |  | 2,283 | ​
Net amortization (1) | ​ |  | (172) | ​ |  | (1,145) | ​ |  | (515) | ​ |  | (3,436) | ​
Net periodic benefit cost | ​ | $ | 1,460 | ​ | $ | 272 | ​ | $ | 4,377 | ​ | $ | 794 | ​
(1) | Interest cost and net amortization are included in the Other expense line item within our condensed consolidated statements of income.

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- Definition Tabular disclosure of the changes in the liability for workers' compensation during the period. + References No definition available. + Details
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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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