Note 1 - Significant Accounting Policies and Related Matters - Computation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic:
Net income available for common stockholders	$ 4,613	$ 5,184	$ 4,624	$ 3,513	$ 6,025	$ 4,314	$ 8,751	$ 3,853	$ 17,934	$ 22,943	$ 17,177
Weighted average shares outstanding (in shares)									19,813	19,426	18,961
Basic earnings per share (in dollars per share)	$ 0.23	$ 0.26	$ 0.23	$ 0.18	$ 0.31	$ 0.22	$ 0.45	$ 0.20	$ 0.91	$ 1.18	$ 0.91
Diluted:
Net income available for common stockholders	$ 4,613	$ 5,184	$ 4,624	$ 3,513	$ 6,025	$ 4,314	$ 8,751	$ 3,853	$ 17,934	$ 22,943	$ 17,177
Weighted average shares outstanding (in shares)									19,813	19,426	18,961
Common stock equivalents, if dilutive (in shares)									513	816	1,072
Shares used in computing diluted earnings per common share (in shares)									20,326	20,242	20,033
Diluted earnings per share (in dollars per share)	$ 0.23	$ 0.25	$ 0.23	$ 0.17	$ 0.30	$ 0.21	$ 0.43	$ 0.19	$ 0.88	$ 1.13	$ 0.86
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)									468	230	6