Note 1 - Significant Accounting Policies and Related Matters - Allowance for Doubtful Accounts and Sales Returns (Details) - Allowance for Doubtful Accounts and Sales Returns [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance	$ 399	$ 349	$ 258
Additions (recoveries) charged to income	388	264	230
Deductions from reserves	265	214	139
Balance	$ 522	$ 399	$ 349