Note 4 - Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Beginning balance	$ 5,506,000	$ 5,200,000	$ 5,200,000
Additions based on tax positions taken in prior years	829,000	306,000
Reductions as a result of a lapse of the applicable statute of limitations	(5,506,000)
Ending balance	$ 829,000	$ 5,506,000	$ 5,200,000