Note 19 - Subsequent Event (Details Textual) - $ / shares	3 Months Ended									12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock, Dividends, Per Share, Declared		$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.80	$ 0.80	$ 0.80
Scenario, Forecast [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.30