Note 2 - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts, beginning of year	$ 135	$ 151	$ 90
Charge (credit) to costs and expenses	33	(13)	93
Deductions	(1)	(3)	(32)
Allowance for doubtful accounts, end of year	$ 167	$ 135	$ 151