Note 6 - Realized Gain (Loss) on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Gross realized gains	$ 2	$ 1	$ 5	$ 6
Gross realized losses				(5)
Total net gains (losses) on AFS securities	$ 2	$ 1	$ 5	$ 1