Note 8 - Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unrecognized tax benefit, beginning of year	$ 2,482	$ 2,482	$ 2,482
Tax positions related to current year	0	0	0
Tax positions related to prior years	0	0	0
Unrecognized tax benefit, end of year	$ 2,482	$ 2,482	$ 2,482