Note 1 - Summary of Significant Accounting Policies - Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Total carrying amount of long-term debt	$ 18,941	$ 22,315
Estimated fair value of long-term debt	18,247	21,668
Fair Value, Recurring [Member]
Assets, fair value	3,615	24,927
Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	3,615	24,927
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Assets, fair value	3,615	24,927
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	$ 3,615	$ 24,927