Note 14 - Earnings Per Share - Computations of Basic and Diluted Earnings 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
Net income									$ 7,900	$ 23,994	$ 38,899
Basic (in shares)	5,751	5,756	5,901	5,921	5,975	6,034	6,159	6,168	5,832	6,083	6,331
Dilutive effect of common stock equivalents (in shares)									48	76	67
Diluted weighted average common shares outstanding (in shares)	5,751	5,799	5,949	5,985	6,029	6,088	6,229	6,264	5,880	6,159	6,398
Basic (in dollars per share)	$ (2.37)	$ 0.80	$ 1.47	$ 1.40	$ 1.02	$ 1.53	$ 1.18	$ 0.22	$ 1.35	$ 3.94	$ 6.14
Diluted (in dollars per share)	$ (2.37)	$ 0.79	$ 1.45	$ 1.39	$ 1.01	$ 1.52	$ 1.17	$ 0.22	$ 1.34	$ 3.90	$ 6.08