Note 8 - Share-based Compensation - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Stock options outstanding, beginning of period (in shares) | shares	41,903,728
Balance, weighted average exercise price, beginning of period (in dollars per share) | $ / shares	$ 0.15
Stock options granted (in shares) | shares	4,413,930
Stock options granted (in dollars per share) | $ / shares	$ 0.90
Stock options exercised (in shares) | shares	(107,153)
Stock options exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 0.20
Stock options cancelled (in shares) | shares	(407,382)
Stock options cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 0.04
Stock options outstanding, end of period (in shares) | shares	45,803,123
Balance, weighted average exercise price, end of period (in dollars per share) | $ / shares	$ 0.22