Note 2 - Summary of Significant Accounting Policies - Estimated Useful Lives of Assets (Details)	3 Months Ended
	Mar. 31, 2021
Operating Lease Assets [Member]
Property and equipment, estimated useful lives (Year)	5 years
Machinery, Manufacturing and Demonstration Equipment [Member] | Minimum [Member]
Property and equipment, estimated useful lives (Year)	3 years
Machinery, Manufacturing and Demonstration Equipment [Member] | Maximum [Member]
Property and equipment, estimated useful lives (Year)	5 years
Computer Equipment [Member]
Property and equipment, estimated useful lives (Year)	3 years
Furniture and Fixtures [Member]
Property and equipment, estimated useful lives (Year)	5 years
Leasehold Improvements [Member]
Leasehold improvements	Lesser of lease term or 3 to 10 years