Note 3 - Revenue From Contracts With Customers - Changes in Contract Liabilities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Total deferred revenue related to contracts with customers, beginning of period	$ 700,000	$ 700,000	$ 700,000	$ 700,000
Deferred revenue related to milestones achieved	0	0	100,000	0
Deferred revenue related to milestones achieved, written off due to contract renegotiations	0	0	(100,000)	0
Total deferred revenue related to contracts with customers, end of period	$ 700,000	$ 700,000	$ 700,000	$ 700,000