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Note 10 - Employee Benefits (Details Textual) - USD ($) |  |  | 1 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Aug. 13, 2020 | May 07, 2019 | May 31, 2023 | Aug. 31, 2022 | May 31, 2022 | May 31, 2021 | May 31, 2020 | May 31, 2019 | Dec. 31, 2018 | Aug. 31, 2018 | May 31, 2018 | Aug. 31, 2017 | May 31, 2017 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 29, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,674,431 |  |  |
Common Stock, Par or Stated Value Per Share |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 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 |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,319,000 | $ 2,814,000 | $ 2,518,000 |
Share-Based Payment Arrangement, Expense, after Tax |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,700,000 | $ 2,200,000 | $ 1,900,000 |
Share Based Compensation Expense Net Of Tax Amount Per Basic Share (in dollars per share) |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.02 | $ 0.03 | $ 0.02 |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number |  |  |  |  |  |  |  |  |  |  |  |  |  | 838,150 | 915,391 |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years 10 months 24 days |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,800,000
Exercisable, shares (in shares) |  |  |  |  |  |  |  |  |  |  |  |  |  | 431,850 |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years 10 months 24 days |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,600,000 |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,100,000 | $ 2,000,000 | $ 789,000 |
Proceeds from Stock Options Exercised |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,400,000 | 4,000,000 | 1,700,000 |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 744,000 | 691,000 | 411,000 |
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, Cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,900,000 | 4,000,000 | 3,000,000 |
Retirement Savings Plan, Participants Less Than 50 Years Old [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount |  |  |  |  |  |  |  |  |  |  |  |  |  | 22,500 |  |  |
Retirement Savings Plan, Participants Over50 Years Old [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,000 |  |  |
Stock Split [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ 0.01 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stockholders' Equity Note, Stock Split, Dividend Settlement, Percent | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  | 838,150 |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 834,000 |  |  |
Performance Shares [Member] | Awards Paid to Employees Upon Vesting [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted |  |  | 114,044 | 21,000 | 102,900 | 98,400 | 73,205 | 45,000 | 3,000 | 3,000 | 42,000 | 3,000 | 65,013 |  |  |  |
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 |  |  |  |  |  |  |  | 60,000 |  |  | 68,550 |  |  |  |  |  |
Unvested Service Based Option Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,800,000 |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
Unvested Performance Unit Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,700,000 |  |  |
Service Based Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares Granted, Value, Share-Based Payment Arrangement, before Forfeiture |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 258,000 | $ 819,000 | $ 1,800,000 |
2015 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized |  | 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 | 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] | Full Value Awards [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized |  | 558,334 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2015 Equity Incentive Plan [Member] | Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted |  |  |  |  |  |  |  |  |  |  |  |  | 163,754 |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  | 226,715 |  |  |
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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