Note 3 - Summary of Significant Accounting Policies (Details Textual)		3 Months Ended		6 Months Ended
	Aug. 30, 2019 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)
Contract with Customer, Liability, Revenue Recognized		$ 130,000	$ 403,000
Contract with Customer, Liability, Current		903,000		$ 903,000	$ 608,000
Contract with Customer, Liability, Noncurrent		1,442,000		1,442,000	$ 1,596,000
Exclusivity Fee [Member]
Contract with Customer, Liability, Revenue Recognized		72,000	$ 143,000
Contract with Customer, Liability, Current		286,000		286,000
Contract with Customer, Liability, Noncurrent		1,191,000		1,191,000
Contract with Customer, Liability, Total	$ 2,000,000	$ 1,477,000		1,477,000
Proceeds from Customers				$ 2,000,000
Supply Agreement [Member]
Supply Agreement, Term (Year)	5 years
Supply Agreement, Renewal Term, Number of Options	2
Supply Agreement, Renewal Term, Per Option (Year)	2 years
Supply Agreement [Member] | Maximum [Member]
Supply Agreement, Renewal Term (Year)	4 years