Note 13 - Employee Equity Incentive Plans - Status of Non-vested Shares (Details) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Shares underlying stock options (in shares)	2,120,000	4,875,000
Weighted average grant date fair value (in dollars per share)	$ 0.24	$ 0.21

Weighted average grant-date fair value of non-vested options outstanding.

No definition available.

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant