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Note 9 - Employee Retirement Plans (Details Textual) - USD ($) $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Apr. 30, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan, Plan Assets, Contributions by Employer |  | $ 1,615 | $ 5,027 | $ 10,546 |
Defined Benefit Plan Concentration Risk Assets Equity Securities Difference Plan Assets And Liabilities |  | 25.00% |  |  |
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year |  | $ 0 |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate |  | 2.50% | 3.50% |  |
Defined Contribution Plan Company Contribution Percentage |  | 3.00% |  |  |
Pension Plan [Member] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  | $ 0 | $ 1,100 | 0 |
Supplemental Employee Retirement Plan [Member] |  |  |  |  |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  | $ 1,600 | 3,200 | 900 |
Supplemental Employee Retirement Plan [Member] | Chief Executive Officer [Member] |  |  |  |  |
Defined Benefit Plan, Benefit Obligation, Payment for Settlement | $ 8,900 |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement | $ (300) |  |  |  |
Postretirement Health Coverage [Member] |  |  |  |  |
Gain (Loss) On Termination Of Post Retirement Benefit Plan |  |  |  | $ 4,000 |
Retirement Plans Contributions [Member] |  |  |  |  |
Defined Contribution Plan Company Contribution Vesting Period (Year) |  | 5 years |  |  |
Defined Contribution Saving Plan, A401 K [Member] |  |  |  |  |
Defined Contribution Plan Company Contribution Vesting Period (Year) |  | 5 years |  |  |
Defined Contribution Plan, Percent, Contributed By Employee Minimum |  | 2.00% |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent |  | 75.00% |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match |  | 8.00% |  |  | 50.00%
Common Stock, Shares Held in Employee Trust, Shares (in shares) |  |  |  | 7,075 |
Multinational Retirement Plan [Member] |  |  |  |  |
Defined Contribution Plan Company Contribution Vesting Period (Year) |  | 5 years |  |  |
Defined Contribution Plan, Percent, Contributed By Employee Minimum |  | 1.00% |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent |  | 50.00% |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match |  | 6.00% |  |  | 50.00%
Merchant Navy Officers Pension Fund [Member] |  |  |  |  |
Postemployment Benefits Liability, Total |  | $ 700 | $ 1,000 |  |
Postemployment Benefits, Period Expense |  | $ 200 |  |  |

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- Definition Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 25 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=109244457&loc=d3e16701-113920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Amount of payment, which decreases benefit obligation of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract. Excludes decreases to benefit obligation for remeasurement due to settlement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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