Note 8 - Accumulated Other Comprehensive (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2018		Mar. 31, 2017	Dec. 31, 2017		Dec. 31, 2016
Balance	$ 127,722	[1]		$ 127,264	[1]	$ 94,106
Comprehensive income (loss)	(2,426)		$ 256	393
AOCI Attributable to Parent [Member]
Balance	(2,744)	[1]	(403)	(266)	[1]	$ (659)
Comprehensive income (loss)	(2,426)		$ 256	$ 393
Reclassification of accumulated other comprehensive income due to tax rate change	$ (52)

[1] Excludes 74 unvested restricted shares