Note 17 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock-based compensation expense before income taxes	$ 2,892	$ 2,473	$ 2,134
Less: deferred tax benefit	(607)	(866)	(747)
Reduction of net income	$ 2,285	$ 1,607	$ 1,387