Note 6 - Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Aug. 31, 2019
Payments of Ordinary Dividends, Common Stock	$ 2,193	$ 1,637
Line Of Credit Facility Dividend Restrictions Percentage Of Net Income Limit			25.00%
Line of Credit Facility, Waiver to Pay Dividends, Maximum			$ 65,000
Paid Quarterly [Member]
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.04	$ 0.03