Note 10 - Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Payments of Ordinary Dividends, Common Stock	$ 3,000			$ 4,098	$ 2,999
Paid Quarterly [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.025	$ 0.015	$ 0.015	$ 0.025