Note 4 - Fair Value Measurement and Fair Value of Financial Instruments - Changes in Contingent Consideration (Details) - Warrants [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Balance at beginning of period	$ 318	$ 338
Additions			341
Adjustment to fair value	(133)	(20)	(3)
Balance at end of period	$ 185	$ 318	$ 338