Note 8 - Treasury Shares (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended				6 Months Ended	90 Months Ended
	Dec. 12, 2018	Aug. 01, 2018	Aug. 12, 2016	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2013	Dec. 31, 2012
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			1,500,000								1,000,000	500,000
Stock Repurchase Program, Additional Shares Authorized			500,000
Treasury Stock, Shares, Ending Balance				1,292,620				1,292,620	1,292,620	1,264,154
Treasury Stock Acquired, Average Cost Per Share									$ 4.85
Treasury Stock, Value, Ending Balance				$ 6,266				$ 6,266	$ 6,266	$ 6,093
Treasury Stock, Shares, Acquired	50,000	100,000						28,466
Treasury Stock, Value, Acquired, Cost Method				$ 149	$ 24	$ 46	$ 36	$ 173