Note 9 - Share-based Compensation - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 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	6,714,410
Stock options granted (in dollars per share) | $ / shares	$ 0.73
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	48,103,603
Balance, weighted average exercise price, end of period (in dollars per share) | $ / shares	$ 0.23