Note 8 - Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Payments of Ordinary Dividends, Common Stock					$ 3,276	$ 2,731
Paid Quarterly [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.03	$ 0.03	$ 0.025	$ 0.025