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EMPLOYEE BENEFIT PLAN (Tables) | 3 Months Ended
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Mar. 31, 2021
EMPLOYEE BENEFIT PLAN |
Schedule of net periodic benefit cost | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended
​ | ​ | March 31,
(in thousands) |  | 2021 |  | 2020
Interest cost |  | $ | 247 |  | $ | 411
Expected return on plan assets |  | ​ | (377) |  | ​ | (395)
Amortization of net losses |  | ​ | 202 |  | ​ | 246
Net periodic benefit cost | ​ | $ | 72 | ​ | $ | 262
Schedule of trading gains (losses) related to SERP assets | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended
​ | ​ | March 31,
(in thousands) |  | 2021 |  | 2020
Trading gains (losses), net | ​ | $ | 471 | ​ | $ | (4,987)

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- Definition Tabular disclosure of selected highly compensated employees to defer a portion of their compensation into the non-qualified Supplemental Retirement Plan ("SERP"). + 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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