Note E - Stock-based Compensation (Details Textual) - USD ($) | May 29, 2014 | Aug. 31, 2020 | Apr. 30, 2020 | Mar. 31, 2020 | Jan. 31, 2020 | Mar. 31, 2019 | Sep. 30, 2020 | Sep. 30, 2019 |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value | | | | | | | $ 636,000 | $ 685,000 |
Allocated Share-based Compensation Expense, Impact on Earnings Per Share, Basic and Diluted (in dollars per share) | | | | | | | $ 0.06 | $ 0.09 |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | $ 2,318,000 | $ 1,228,000 |
Amortization, Current Year [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 130,000 | |
Amortization, Next Year [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 513,000 | |
Amortization Year 2 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 513,000 | |
Amortization, Year 3 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 358,000 | |
Amortization, Year 4 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 271,000 | |
Amortization, Year 5 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 200,000 | |
Amortization, Year 6 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 200,000 | |
Amortization, Year 7 [Member] | | | | | | | | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | 133,000 | |
Salaries, Wages and Benefits [Member] | | | | | | | | |
Share-based compensation | | | | | | | 430,000 | 736,000 |
Director [Member] | Salaries, Wages and Benefits [Member] | | | | | | | | |
Share-based compensation | | | | | | | $ 90,000 | $ 100,000 |
Restricted Stock [Member] | | | | | | | | |
Number of Common Stock Accrued Under Share-based Compensation Plan (in shares) | | | | | | | 63,182 | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | | | | | | | $ 36.46 | |
Share-based compensation | | | | | | $ 90,000 | | |
The 2014 Stock Option Plan [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares) | 750,000 | | | | | | | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Key Employees [Member] | | | | | | | | |
Number of Common Stock Accrued Under Share-based Compensation Plan (in shares) | | 13,332 | | | 7,000 | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | | $ 30.25 | | | $ 56.45 | | | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Director [Member] | | | | | | | | |
Number of Common Stock Accrued Under Share-based Compensation Plan (in shares) | | | 242 | 2,608 | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | | | $ 41.40 | $ 30.75 | | | | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | | | | | | | | |
Number of Common Stock Accrued Under Share-based Compensation Plan (in shares) | | 40,000 | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | | $ 35.37 | | | | | | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2022 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | $ 5,000 | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2025 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | 10,000 | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2023 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | 5,000 | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2024 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | 5,000 | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2027 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | 5,000 | |
The 2014 Stock Option Plan [Member] | Stock Award [Member] | Chief Executive Officer [Member] | Vesting In 2026 [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Number of Shares | | | | | | | $ 10,000 | |
The 2014 Stock Option Plan [Member] | Minimum [Member] | Restricted Stock [Member] | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | 85.00% | | | | | | | |