Note 4 - Property and Equipment, Net (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment, Net, Ending Balance	$ 65,959		$ 65,959		$ 64,850
Depreciation, Depletion And Amortization, Excluding Intangible Asset Amortization	6,900	$ 6,400	14,200	$ 12,600
Scanner Appliances and Other Computer Equipment Subject To Subscription [Member]
Property, Plant and Equipment, Net, Ending Balance	7,300		7,300		7,500
Scanner Appliances and Other Computer Equipment Not Placed In Service [Member]
Property, Plant and Equipment, Net, Ending Balance	$ 2,200		$ 2,200		$ 1,900