Note 4 - Stock-based Compensation Plans (Details Textual) | | | | | | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | |
Jul. 01, 2023 shares | Mar. 01, 2023 shares | Jan. 03, 2023 shares | Feb. 04, 2022 $ / shares shares | Jul. 01, 2021 USD ($) | Jul. 31, 2022 shares | Apr. 30, 2021 shares | Sep. 30, 2023 USD ($) | Sep. 30, 2022 USD ($) | Sep. 30, 2023 USD ($) shares | Sep. 30, 2022 USD ($) | Dec. 31, 2022 shares | Jul. 10, 2019 shares |
Share-based Payment Arrangement, Expense | $ | | | | | | | | $ 652,000 | $ 492,000 | $ 1,142,000 | $ 1,348,000 | | |
Water Supply Agreement, Number of Acre-feet of Water Per Annum To Customer | | | | | | | 9,500 | | | | | | |
Restricted Stock Units (RSUs) [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Accelerated Vesting, Number (in shares) | | | | 170,000 | | | | | | | | | |
Restricted Stock Units (RSUs) [Member] | Vesting Upon Completion of Final Binding Water Supply Agreement [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Accelerated Vesting, Number (in shares) | | | | 85,000 | | | | | | | | | |
Restricted Stock Units (RSUs) [Member] | Vesting on March 1, 2023 [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Accelerated Vesting, Number (in shares) | | | | 85,000 | | | | | | | | | |
Restricted Stock Units (RSUs) [Member] | Share-Based Payment Arrangement, Employee [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 825,000 | | | | | | |
Milestone RSUs [Member] | Share-Based Payment Arrangement, Employee [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 510,000 | | | | | | |
Milestone RSUs [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 255,000 | | | | | | |
Milestone RSUs [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Tranche Two [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 255,000 | | | | | | |
Non-milestone Restricted Stock Units (RSUs) [Member] | Share-Based Payment Arrangement, Employee [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 315,000 | | | | | | |
Non-milestone Restricted Stock Units (RSUs) [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Tranche One [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | 60,000 | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | | | 60,000 | | | | | | | | | | |
Non-milestone Restricted Stock Units (RSUs) [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Tranche Two [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period (in shares) | | 158,673 | | | | | | | | | | 158,673 | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | | | | | | | 255,000 | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | | 255,000 | | | | | | | | | | | |
Performance Stock Units [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted (in shares) | | | | 450,000 | | | | | | | | | |
Performance Stock Units [Member] | Vesting Upon Price Hurdle of $7 Per Share [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted (in shares) | | | | 200,000 | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vesting, Price Hurdle (in dollars per share) | $ / shares | | | | $ 7 | | | | | | | | | |
Performance Stock Units [Member] | Vesting Upon Price Hurdle of $9 Per Share [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted (in shares) | | | | 150,000 | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vesting, Price Hurdle (in dollars per share) | $ / shares | | | | $ 9 | | | | | | | | | |
Performance Stock Units [Member] | Vesting Upon Price Hurdle of $11 Per Share [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted (in shares) | | | | 50,000 | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vesting, Price Hurdle (in dollars per share) | $ / shares | | | | $ 11 | | | | | | | | | |
Performance Stock Units [Member] | Vesting Upon Price Hurdle of $13 Per Share [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Granted (in shares) | | | | 50,000 | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vesting, Price Hurdle (in dollars per share) | $ / shares | | | | $ 13 | | | | | | | | | |
A Consultant [Member] | Restricted Stock Units (RSUs) [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) | 400,000 | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares) | 200,000 | | | | | | | | | | | | |
A Consultant [Member] | Restricted Stock Units (RSUs) [Member] | Vesting Upon Completion of Certain Milestone [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | 200,000 | | | | | | | | | | | | |
A Consultant [Member] | Restricted Stock Units (RSUs) [Member] | Vesting on October 1, 2023 [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | 100,000 | | | | | | | | | | | | |
A Consultant [Member] | Restricted Stock Units (RSUs) [Member] | Vesting on February 1, 2024 [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) | 100,000 | | | | | | | | | | | | |
Two Thousand Nineteen Equity Incentive Plan [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares) | | | | | | | | | | | | | 2,700,000 |
Two Thousand Nineteen Equity Incentive Plan [Member] | Outside Director [Member] | Accrues Yearly [Member] | | | | | | | | | | | | | |
Salary and Wage, Officer, Excluding Cost of Good and Service Sold | $ | | | | | $ 75,000 | | | | | | | | |
Share-based Payment Arrangement, Expense | $ | | | | | 25,000 | | | | | | | | |
Two Thousand Nineteen Equity Incentive Plan [Member] | Outside Director [Member] | Accrues Quarterly [Member] | | | | | | | | | | | | | |
Salary and Wage, Officer, Excluding Cost of Good and Service Sold | $ | | | | | 18,750 | | | | | | | | |
Share-based Payment Arrangement, Expense | $ | | | | | $ 6,250 | | | | | | | | |
Two Thousand Nineteen Equity Incentive Plan [Member] | Directors, Consultants and Employees [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period (in shares) | | | | | | | | | | 2,312,925 | | | |
Two Thousand Nineteen Equity Incentive Plan [Member] | Director [Member] | | | | | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period (in shares) | | | | | | | | | | 46,744 | | | |