Note 8 - Income Taxes - Change in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance at January 1	$ 8,498	$ 8,706	$ 8,345
Deferred tax liabilities assumed through acquisitions	(8,498)	(3,297)	(1,541)
Charged to income tax expense	2,493	3,089	1,902
Balance at December 31	$ 2,493	$ 8,498	$ 8,706