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Employee benefit plans (Tables) | 6 Months Ended
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Jun. 30, 2020
Employee benefit plans |
Schedule of components of net periodic benefit cost | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​
​ | ​ | Pension Benefits
Three Months Ended June 30, |  | 2020 |  | 2019
Components of net periodic pension benefit: |  | ​ | ​ |  | ​ | ​
Interest cost | ​ | $ | 163 | ​ | $ | 192
Expected return on plan assets | ​ |  | (371) | ​ |  | (325)
Amortization of unrecognized net gain | ​ |  | 65 | ​ |  | 68
Net periodic benefit | ​ | $ | (143) | ​ | $ | (65)
​ | ​ | ​
​ | ​ | Pension Benefits
Six Months Ended June 30, |  | 2020 |  | 2019
Components of net periodic pension cost: |  | ​ | ​ |  | ​ | ​
Interest cost | ​ | $ | 217 | ​ | $ | 320
Expected return on plan assets | ​ |  | (494) | ​ |  | (542)
Amortization of unrecognized net gain | ​ |  | 87 | ​ |  | 113
Net periodic benefit cost | ​ | $ | (190) | ​ | $ | (109)

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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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