Note 3 - Stock-based Compensation (Details Textual) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares, Ending Balance (in shares)	0	0	0	0
Share-based Payment Arrangement, Expense	$ 292,000	$ (75,000)	$ 389,000	$ (188,000)
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent	887,000	$ 289,000	887,000	$ 289,000
Restricted Stock [Member]
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount	$ 657,000		$ 657,000
Restricted Stock [Member] | Forecast [Member]
Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount					$ 25,000	$ 188,000	$ 317,000	$ 127,000