Note 3 - Goodwill and Acquired Intangible Assets (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Asset, Useful Life	7 years
Amortization of Intangible Assets, Total	$ 503	$ 212	$ 212
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	912
Finite-Lived Intangible Assets, Amortization Expense, Year Two	912
Finite-Lived Intangible Assets, Amortization Expense, Year Three	912
Finite-Lived Intangible Assets, Amortization Expense, Year Four	912
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 912