Note 2 - Summary of Significant Accounting Policies - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Basic shares (in shares)									6,276,670	6,173,450
Dilutive shares (in shares)									377,951
Diluted shares (in shares)									6,654,621	6,173,450
Net income (loss)	$ 1,477	$ 240	$ 359	$ 414	$ (1,866)	$ 635	$ 416	$ 404	$ 2,490	$ (411)
Basic net income (loss) per share (in dollars per share)	$ 0.23	$ 0.04	$ 0.06	$ 0.07	$ (0.30)	$ 0.10	$ 0.07	$ 0.07	$ 0.40	$ (0.07)
Diluted net income (loss) per share (in dollars per share)	$ 0.22	$ 0.03	$ 0.06	$ 0.06	$ (0.30)	$ 0.10	$ 0.06	$ 0.06	$ 0.37	$ (0.07)