Note 10 - Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Payments of Ordinary Dividends, Common Stock	$ 2,731	$ 1,635
Paid Quarterly [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.025	$ 0.015