Note 5 - Goodwill and Acquired Intangible Assets (Details Textual) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Number of Reporting Units	1
Goodwill, Ending Balance	$ 2,483	$ 2,483
Disposal Group, Including Discontinued Operation, Goodwill	$ 1,500
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	12 years
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 100
Finite-Lived Intangible Assets, Amortization Expense, Year Two	100
Finite-Lived Intangible Assets, Amortization Expense, Year Three	100
Finite-Lived Intangible Assets, Amortization Expense, Year Four	100
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 100