Note 1 - Summary of Significant Accounting Policies - Share-based Compensation Amounts Recognized in Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-cash share-based compensation expense	$ 1,845	$ 1,929	$ 1,383
Amount of related income tax benefit	(2,310)	(1,164)	(505)
Net (benefit) expense to net income	$ (465)	$ 765	$ 878