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Note 9 - Employee Retirement Plans - Pension Plan Measured at Fair Value (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | --- | ---
Fair value of plan assets | $ 56,495 | $ 59,625 | $ 56,790 | $ 57,536
Pension Plan [Member] |  |  |  |
Total |  | 59,095 |  |
Accrued income |  | 530 |  |
Pension Plan [Member] | Change In Plan Assets [Member] |  |  |  |
Fair value of plan assets | 56,495 | 59,625 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Total |  | 6,569 |  |
Accrued income |  | 530 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Change In Plan Assets [Member] |  |  |  |
Fair value of plan assets | 39,705 | 7,099 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Total |  | 52,526 |  |
Accrued income |  | 0 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Change In Plan Assets [Member] |  |  |  |
Fair value of plan assets | 1,626 | 52,526 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Total |  | 0 |  |
Accrued income |  | 0 |  |
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Change In Plan Assets [Member] |  |  |  |
Fair value of plan assets | 0 | 0 |  |
Pension Plan [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Change In Plan Assets [Member] |  |  |  |
Fair value of plan assets | 15,164 |  |  |
Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] |  |  |  |
Fair value of plan assets | 24,947 | 699 |  |
Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets | 21,780 | 699 |  |
Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets | 0 | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets | 0 | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Equity Securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |  |
Fair value of plan assets | 3,167 | 0 |  |
Total |  | 0 |  |
Accrued income |  | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Debt Security [Member] |  |  |  |
Fair value of plan assets | 29,922 |  |  |
Pension Plan [Member] | Defined Benefit Plan, Debt Security [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets | 17,925 |  |  |
Pension Plan [Member] | Defined Benefit Plan, Debt Security [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets | 0 |  |  |
Pension Plan [Member] | Defined Benefit Plan, Debt Security [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets | 0 |  |  |
Pension Plan [Member] | Defined Benefit Plan, Debt Security [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |  |
Fair value of plan assets | 11,997 |  |  |
Pension Plan [Member] | US Government Agencies Debt Securities [Member] |  |  |  |
Fair value of plan assets |  | 5,870 |  |
Pension Plan [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets |  | 5,870 |  |
Pension Plan [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |  |  |
Fair value of plan assets | 1,626 | 2,526 |  |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets | 0 | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets | 1,626 | 2,526 |  |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets | 0 | 0 |  |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |  |
Fair value of plan assets | $ 0 |  |  |
Pension Plan [Member] | Collateralized Mortgage Backed Securities [Member] |  |  |  |
Fair value of plan assets |  | 765 |  |
Pension Plan [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets |  | 765 |  |
Pension Plan [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Corporate Debt Securities [Member] |  |  |  |
Fair value of plan assets |  | 47,839 |  |
Pension Plan [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets |  | 47,839 |  |
Pension Plan [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Defined Benefit Plan Other Asset [Member] |  |  |  |
Fair value of plan assets |  | 1,396 |  |
Pension Plan [Member] | Defined Benefit Plan Other Asset [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |
Fair value of plan assets |  | 0 |  |
Pension Plan [Member] | Defined Benefit Plan Other Asset [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |
Fair value of plan assets |  | 1,396 |  |
Pension Plan [Member] | Defined Benefit Plan Other Asset [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |
Fair value of plan assets |  | $ 0 |  |

X
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