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						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income	$ 6,504	$ 8,299	$ 5,929	$ 7,513	$ 3,500	$ 3,174	$ 20,732	$ 14,187
Weighted average shares outstanding (in shares)	21,592			20,254			20,920	20,201
Basic earnings per share (in dollars per share)	$ 0.30			$ 0.37			$ 0.99	$ 0.70
Common stock equivalents, if dilutive (in shares)	343			220			331	233
Shares used in computing diluted earnings per common share (in shares)	21,935			20,474			21,251	20,434
Diluted earnings per share (in dollars per share)	$ 0.30			$ 0.37			$ 0.98	$ 0.69
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)	0			496			1	610