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Note 10 - Employee Benefits (Details Textual) |  |  | 1 Months Ended | 12 Months Ended
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Aug. 13, 2020 $ / shares shares | May 07, 2019 shares | May 31, 2024 shares | May 31, 2023 shares | Aug. 31, 2022 shares | May 31, 2022 shares | May 31, 2021 shares | May 31, 2020 shares | May 31, 2019 shares | Dec. 31, 2018 shares | Aug. 31, 2018 shares | May 31, 2018 shares | Dec. 31, 2024 USD ($) $ / shares shares | Dec. 31, 2023 USD ($) $ / shares shares | Dec. 31, 2022 USD ($) $ / shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted | shares |  |  |  |  |  |  |  |  |  |  |  |  | 2,781,347 |  |
Common Stock, Par or Stated Value Per Share | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.01 | $ 0.01 |
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Forfeiture Rate Of Unvested Outstanding Awards |  |  |  |  |  |  |  |  |  |  |  |  | 1.25% |  |
Share-Based Payment Arrangement, Expense |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,236,000 | $ 2,319,000 | $ 2,814,000
Share-Based Payment Arrangement, Expense, after Tax |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,700,000 | $ 1,700,000 | $ 2,200,000
Share Based Compensation Expense Net Of Tax Amount Per Basic Share (in dollars per share) | $ / shares |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.02 | $ 0.02 | $ 0.03
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number | shares |  |  |  |  |  |  |  |  |  |  |  |  | 704,421 | 838,150 |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term |  |  |  |  |  |  |  |  |  |  |  |  | 3 years 3 months 18 days |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 339,000 |  |
Exercisable, shares (in shares) | shares |  |  |  |  |  |  |  |  |  |  |  |  | 441,921 |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term |  |  |  |  |  |  |  |  |  |  |  |  | 2 years 8 months 12 days |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 332,000 |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  | 521,000 | $ 1,100,000 | $ 2,000,000
Proceeds from Stock Options Exercised |  |  |  |  |  |  |  |  |  |  |  |  | 1,800,000 | 2,400,000 | 4,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 599,000 | 744,000 | 691,000
Defined Contribution Plan, Employer Matching Contribution, Percent of Match |  |  |  |  |  |  |  |  |  |  |  |  | 35.00% |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  |  |  |  |  |  |  |  |  |  |  |  | 6.00% |  |
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |
Defined Contribution Plan, Employer Discretionary Contribution Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 0 | 0 | 0
Defined Contribution Plan, Cost |  |  |  |  |  |  |  |  |  |  |  |  | 3,400,000 | 3,900,000 | 4,000,000
Retirement Savings Plan, Participants Less Than 50 Years Old [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount |  |  |  |  |  |  |  |  |  |  |  |  | 23,000 |  |
Retirement Savings Plan, Participants Over50 Years Old [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,500 |  |
Stock Split To [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stockholders' Equity Note, Stock Split, Conversion Ratio | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Split from [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stockholders' Equity Note, Stock Split, Conversion Ratio | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Split [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ / shares | $ 0.01 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stockholders' Equity Note, Stock Split, Dividend Settlement, Percent | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding | shares |  |  |  |  |  |  |  |  |  |  |  |  | 704,421 |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value |  |  |  |  |  |  |  |  |  |  |  |  | $ 901,000 |  |
Performance Shares [Member] | Awards Paid to Employees Upon Vesting [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted | shares |  |  | 125,464 | 114,044 | 21,000 | 102,900 | 98,400 | 73,205 | 45,000 | 3,000 | 3,000 | 42,000 |  |  |
Performance Shares [Member] | One Half of Awards Paid Immediately Upon Vesting and One Half Credited to Employees' Accounts [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted | shares |  |  |  |  |  |  |  |  | 60,000 |  |  |  |  |  |
Unvested Service Based Option Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,200,000 |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition |  |  |  |  |  |  |  |  |  |  |  |  | 2 years 4 months 24 days |  |
Unvested Performance Unit Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,800,000 |  |
Service Based Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares Granted, Value, Share-Based Payment Arrangement, before Forfeiture |  |  |  |  |  |  |  |  |  |  |  |  | $ 147,000 | $ 258,000 | $ 819,000
2015 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized | shares |  | 1,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
2015 Equity Incentive Plan [Member] | Stock Split [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized | shares | 3,950,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
2015 Equity Incentive Plan [Member] | Share-Based Payment Arrangement, Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Annual Percentage Of Award Which Vests |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% |  |
2015 Equity Incentive Plan [Member] | Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted | shares |  |  |  |  |  |  |  |  |  |  |  | 68,550 |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding | shares |  |  |  |  |  |  |  |  |  |  |  |  | 298,791 |  |
2015 Equity Incentive Plan [Member] | Full Value Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized | shares |  | 558,334 |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum [Member] | 2015 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period |  |  |  |  |  |  |  |  |  |  |  |  | 7 years |  |
Maximum [Member] | 2015 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |

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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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