Note 11 - Stock-based Compensation Plan (Details Textual) $ / shares in Units, $ in Thousands | | | | | | | | | 1 Months Ended | 3 Months Ended | 12 Months Ended | 15 Months Ended |
Mar. 06, 2024 USD ($) shares | Jan. 16, 2024 USD ($) shares | May 08, 2023 USD ($) shares | Mar. 08, 2023 USD ($) shares | Mar. 09, 2022 USD ($) shares | Mar. 08, 2022 | Oct. 01, 2021 shares | Mar. 10, 2021 shares | Aug. 31, 2020 | Mar. 31, 2024 USD ($) $ / shares shares | Dec. 31, 2023 | Mar. 31, 2023 USD ($) $ / shares shares | Dec. 31, 2023 | Mar. 31, 2024 USD ($) shares |
Share-Based Payment Arrangement, Amount Capitalized | $ | | | | | | | | | | $ 0 | | $ 0 | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares | | | | | | | | | | $ 6.55 | | $ 9.32 | | |
Number of Operating Segments | | | | 2 | | | | | | 3 | | | | |
Share-Based Payment Arrangement, Option [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year) | | | | | | | | | | 10 years | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | | | | | | | | | | | | | | 4 years |
Restricted Stock [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | | | | 138,838 | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | | | | | | | | | | 39,790 | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $ | | | | | | | | | | $ 463 | | $ 381 | | |
Restricted Stock [Member] | Employees [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | | | | | | | | | | 4 years | | | | |
Restricted Stock [Member] | Independent Directors [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) | | | | | | | | | | 1 year | | | | |
Restricted Stock [Member] | Independent Directors [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 25% | | | | |
Performance-Based Restricted Stock [Member] | Members of The Senior Management [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 5,000 | 18,000 | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested Options Forfeited, Number of Shares (in shares) | | | | | | | | | | | | 6,000 | | |
Performance-Based Restricted Stock [Member] | Members of The Senior Management [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 75% | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares) | | | | | | | | | | 6,000 | | | | 6,000 |
Performance-Based Restricted Stock [Member] | Members of The Senior Management [Member] | Share-Based Payment Arrangement, Vesting on Third Anniversary of Grant Date [Member] | | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | | | | | | | | | | 12,000 | | | | |
Performance-Based Restricted Stock [Member] | Members of The Senior Management [Member] | Share-Based Payment Arrangement, Tranche Two [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 100% | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number (in shares) | | | | | | | | | | 6,000 | | | | 6,000 |
Performance-Based Restricted Stock [Member] | Members of The Senior Management [Member] | Vesting on January 1, 2025, Based on Performance Metrics [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 0% | | | 50% | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | | | | | | | 0% | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | | | | | | | 150% | | | | | | | |
Performance-Based Restricted Stock [Member] | Chief Executive Officer and Chief Financial Officer [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | | | | | 0% | 0% | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | | | | | 150% | 150% | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | 18,888 | 20,493 | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted, Fair Value | $ | | | | $ 303 | $ 200 | | | | | | | | | |
Performance-Based Restricted Stock [Member] | Chief Executive Officer and Chief Financial Officer [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 100% | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Probable Final Vesting Percentage | | | | | | | | | | 0% | 50% | | | |
Performance-Based Restricted Stock [Member] | President of Environmental Technologies [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | | | 0% | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | | | 150% | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | 5,081 | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted, Fair Value | $ | | | $ 108 | | | | | | | | | | | |
Performance-Based Restricted Stock [Member] | President of Environmental Technologies [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 100% | | | | |
Performance-Based Restricted Stock [Member] | President of Process Technologies [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | 8,231 | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted, Fair Value | $ | | $ 100 | | | | | | | | | | | | |
Performance-Based Restricted Stock [Member] | President of Process Technologies [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | | 0% | | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | | 150% | | | | | | | | | | | | |
Performance-Based Restricted Stock [Member] | Chief Executive Officer, Chief Financial Officer, and Division Presidents [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | 33,539 | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted, Fair Value | $ | $ 380 | | | | | | | | | | | | | |
Performance-Based Restricted Stock [Member] | Chief Executive Officer, Chief Financial Officer, and Division Presidents [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | | 100% | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | 0% | | | | | | | | | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | 150% | | | | | | | | | | | | | |
The 2023 Stock Incentive Plan [Member] | | | | | | | | | | | | | | |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount | $ | | | | | | | | | | $ 4,813 | | | | $ 4,813 |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | | | | | | | | | | 2 years 6 months | | | | |
Restricted Stock Vesting in Three Years [Member] | Restricted Stock [Member] | Vesting Based On Performance Metrics [Member] | | | | | | | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | | | | | | | | | 100% | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Lower Range | | | | | | | | | 0% | | | | | |
Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting Rights Percentage Upper Range | | | | | | | | | 150% | | | | | |