Note 11 - Net Income per Share - Computation of Basic and Diluted Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic:
Net income	$ 3,500	$ 3,174	$ 4,624	$ 3,513	$ 6,674	$ 8,137
Weighted average shares outstanding (in shares)	20,180		19,680		20,174	19,660
Basic earnings per share (in dollars per share)	$ 0.17		$ 0.23		$ 0.33	$ 0.41
Diluted:
Net income	$ 3,500	$ 3,174	$ 4,624	$ 3,513	$ 6,674	$ 8,137
Weighted average shares outstanding (in shares)	20,180		19,680		20,174	19,660
Common stock equivalents, if dilutive (in shares)	219		566		241	566
Shares used in computing diluted earnings per common share (in shares)	20,399		20,246		20,415	20,226
Diluted earnings per share (in dollars per share)	$ 0.17		$ 0.23		$ 0.33	$ 0.40
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)	713		531		651	537