Note 1 - Summary of Significant Accounting Policies - Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Total carrying amount of long-term debt	$ 33,321	$ 34,281
Estimated fair value of long-term debt	35,246	35,205
Fair Value, Recurring [Member]
Assets, fair value	2,739	3,662
Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	2,739	3,662
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Assets, fair value	2,739	3,662
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value	2,739	3,662
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Assets, fair value
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] | Fair Value, Recurring [Member]
Assets, fair value