Note 15 - Segment Information (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Number of Operating Segments			1
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 53,927	$ 39,794	$ 138,071	$ 105,411
UNITED STATES
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 24,200	$ 18,200	$ 62,300	$ 46,400
Revenue from Contract with Customer Benchmark [Member] | Customer Concentration Risk [Member]
Number of Major Customers	0	0	0	0