Note 2 - Revenue Recognition - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Deferred revenue	$ 1,887	$ 2,574
Increases due to consideration received from customers	736	2,255
Revenue recognized	(952)	(2,883)
Deferred revenue	1,671	1,946
Unbilled receivables - beginning of period	271	72
Increases due to revenue recognized, not invoiced to customers	1,461	2,223
Decreases due to customer invoicing	(1,509)	(2,004)
Unbilled receivables - end of period	$ 223	$ 291