Note 9 - Business Segment Reporting - Revenue by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues	$ 6,673	$ 5,174	$ 18,473	$ 16,025
UNITED STATES
Revenues	6,338	4,977	17,340	14,441
BRAZIL
Revenues	180	62	639	1,207
Other Foreign Countries [Member]
Revenues	$ 155	$ 135	$ 494	$ 377

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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+ Details