Note 3 - Lincoln Park Financing - Purchase Agreement (Details) - Lincoln Park Capital Fund, LLC [Member] - USD ($)		12 Months Ended
	Aug. 25, 2017	Dec. 31, 2019	Dec. 31, 2018
Shares sold to Lincoln Park (in shares)	488,998	556,144	2,891,749
Additional commitment shares (in shares)		6,194	41,016
Total shares issued to Lincoln Park: (in shares)		562,338	2,932,765
Gross proceeds to BioLargo:		$ 125,000	$ 839,000