Note 13 - Employee Equity Incentive Plans - Weighted Average Grant Date Fair Value Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Stock options granted during the period (in dollars per share)	$ 0.23	$ 0.21
Stock options vested during the period (in dollars per share)	0.22	0.20
Stock options forfeited during the period (in dollars per share)	$ 0.19	$ 0.13

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration