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, 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	Dec. 31, 2016
Basic:
Net income available for common stockholders	$ 6,025	$ 4,314	$ 8,751	$ 3,853	$ 4,284	$ 5,042	$ 4,632	$ 3,219	$ 22,943	$ 17,177	$ 10,590
Weighted average shares outstanding (in shares)									19,426	18,961	18,485
Basic earnings per share (in dollars per share)	$ 0.31	$ 0.22	$ 0.45	$ 0.20	$ 0.22	$ 0.26	$ 0.25	$ 0.17	$ 1.18	$ 0.91	$ 0.57
Diluted:
Net income available for common stockholders	$ 6,025	$ 4,314	$ 8,751	$ 3,853	$ 4,284	$ 5,042	$ 4,632	$ 3,219	$ 22,943	$ 17,177	$ 10,590
Weighted average shares outstanding (in shares)									19,426	18,961	18,485
Common stock equivalents, if dilutive (in shares)									816	1,072	756
Shares used in computing diluted earnings per common share (in shares)									20,242	20,033	19,241
Diluted earnings per share (in dollars per share)	$ 0.30	$ 0.21	$ 0.43	$ 0.19	$ 0.21	$ 0.25	$ 0.23	$ 0.16	$ 1.13	$ 0.86	$ 0.55
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive (in shares)									230	6	45