Note 1 - Business and Organization (Details Textual)		3 Months Ended		12 Months Ended
		Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total		$ (2,749,000)	$ (2,429,000)
Net Cash Provided by (Used in) Operating Activities, Total		(869,000)	(996,000)
Working Capital		2,343,000
Assets, Current, Total		782,000		$ 955,000
Revenue from Contract with Customer, Including Assessed Tax		$ 364,000	364,000	1,364,000
Number of Reportable Segments		2
Convertible Notes Payable, Current		$ 2,072,000		1,365,000
Cash Provided by Financing Activities		730,000
Cash and Cash Equivalents, at Carrying Value, Ending Balance		$ 512,000	$ 921,000	655,000	$ 990,000
Number of Wholly-Owned Subsidiaries		5
Clyra Medical Technology Inc [Member] | Biolargo [Member]
Noncontrolling Interest, Ownership Percentage by Parent		42.00%
Notes Payable, Maturing June 6, 2019 [Member]
Convertible Notes Payable, Current		$ 440,000
Line of Credit, Maturing September 1, 2019 [Member]
Long-term Line of Credit, Total	[1]	430,000		$ 430,000
Convertible Notes Payable [Member]
Short-term Debt, Total		$ 2,072,000

[1] See Note 14 "Subsequent Events"