Note 7 - Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	May 31, 2022	May 31, 2013
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value	$ 199,000	$ 7,000
Share-Based Payment Arrangement, Expense, Tax Benefit	7,000	7,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value	532,000	331,000
Share-Based Payment Arrangement, Expense	88,000	87,000
Proceeds from Stock Options Exercised	359,000	137,000
Share-Based Payment Arrangement, Exercise of Option, Tax Benefit	69,000	49,000
Restricted Stock Units (RSUs) [Member]
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 92,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	10 months 24 days
Share-Based Payment Arrangement, Expense	$ 12,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	3,033
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)	$ 34.07
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	1 year
Restricted Stock [Member]
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 0
Share-Based Payment Arrangement, Expense		$ 12,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)				1,650
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)				$ 31
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)				1 year
Stock Option Plan 2022 [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)					576,550
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)	107,200
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 1,700,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	4 years 2 months 12 days
Stock Option Plan 2013 [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					126,550
Common Stock, Capital Shares Reserved for Future Issuance (in shares)						141,752
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)			0
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 0