Note 1 - Summary of Significant Accounting Policies - Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Total carrying amount of long-term debt	$ 35,166	$ 36,787
Estimated fair value of long-term debt	34,723	36,403
Fair Value, Recurring [Member]
Assets, fair value	1,504	6,471
Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	1,504	6,471
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Assets, fair value	1,504	6,471
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	$ 1,504	$ 6,471