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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic:
Net income available for common stockholders	$ 7,033	$ 7,513	$ 3,500	$ 3,174	$ 4,613	$ 5,184	$ 4,624	$ 3,513	$ 21,220	$ 17,934	$ 22,943
Weighted average shares outstanding (in shares)									20,246	19,813	19,426
Basic earnings per share (in dollars per share)	$ 0.35	$ 0.37	$ 0.17	$ 0.16	$ 0.23	$ 0.26	$ 0.23	$ 0.18	$ 1.05	$ 0.91	$ 1.18
Diluted:
Net income available for common stockholders	$ 7,033	$ 7,513	$ 3,500	$ 3,174	$ 4,613	$ 5,184	$ 4,624	$ 3,513	$ 21,220	$ 17,934	$ 22,943
Weighted average shares outstanding (in shares)									20,246	19,813	19,426
Common stock equivalents, if dilutive (in shares)									233	513	816
Shares used in computing diluted earnings per common share (in shares)									20,479	20,326	20,242
Diluted earnings per share (in dollars per share)	$ 0.34	$ 0.37	$ 0.17	$ 0.16	$ 0.23	$ 0.25	$ 0.23	$ 0.17	$ 1.04	$ 0.88	$ 1.13
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)									483	468	230