Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals)	3 Months Ended	12 Months Ended
	Mar. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	18,302,880	18,228,887
Common stock, shares outstanding (in shares)	18,302,880	18,228,887
Reverse Stock Split [Member]
Common stock, reverse stock split 4-to-1	4