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COMPONENTS OF PENSION PLAN NET PERIODIC BENEFIT COSTS | 6 Months Ended
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Jun. 30, 2020
EMPLOYEE BENEFIT PLANS |
COMPONENTS OF PENSION PLAN NET PERIODIC BENEFIT COSTS | 17.COMPONENTS OF PENSION PLAN NET PERIODIC BENEFIT COSTS ​ Eligible employees at certain of our mining operations participate in a defined benefit plan (the "Pension Plan") that we sponsor. The Pension Plan is currently closed to new applicants and participants in the Pension Plan are no longer receiving benefit accruals for service. The benefit formula for the Pension Plan is a fixed dollar unit based on years of service. Components of the net periodic benefit cost for each of the periods presented are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Three Months Ended | ​ | Six Months Ended | ​
​ | ​ | June 30, | ​ | June 30, | ​
​ | ​ | 2020 |  | 2019 |  | 2020 |  | 2019 |
​ | ​ | (in thousands) | ​
Interest cost | ​ | $ | 1,054 | ​ | $ | 1,216 | ​ | $ | 2,108 | ​ | $ | 2,432 | ​
Expected return on plan assets | ​ |  | (1,491) | ​ |  | (1,234) | ​ |  | (2,983) | ​ |  | (2,466) | ​
Amortization of prior service cost | ​ | ​ | 47 | ​ | ​ | 46 | ​ | ​ | 93 | ​ | ​ | 93 | ​
Amortization of net loss | ​ |  | 1,063 | ​ |  | 982 | ​ |  | 2,127 | ​ |  | 1,961 | ​
Net periodic benefit cost (1) | ​ | $ | 673 | ​ | $ | 1,010 | ​ | $ | 1,345 | ​ | $ | 2,020 | ​
| (1) | Net periodic benefit cost for the Pension Plan is included in the Other expense line item within our condensed consolidated statements of income.
​ During the six months ended June 30, 2020, we made a contribution payment of $1.1 million to the Pension Plan for the 2019 plan year. We expect to defer all remaining contributions to the Pension Plan during 2020 until January 2021 as provided for under the Coronavirus Aid Relief and Economic Security Act of 2020 enacted in response to the COVID-19 pandemic.

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- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
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