Note 11 - Summary of Information about Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Price Range 1 [Member]
Option Awards Outstanding,Covered Shares Exercised (in shares) | shares	1,596,186
Option Awards Outstanding, Weighted Average Remaining Contractual Life	3 years 233 days
Option Awards Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 0.55
Option Awards Exercisable, Covered Shares Exercisable (in shares) | shares	1,596,186
Option Awards Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.55
Price Range 2 [Member]
Option Awards Outstanding,Covered Shares Exercised (in shares) | shares	942,808
Option Awards Outstanding, Weighted Average Remaining Contractual Life	6 years 248 days
Option Awards Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 1.42
Option Awards Exercisable, Covered Shares Exercisable (in shares) | shares	717,755
Option Awards Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 1.35
Exercise Prices, Lower Range (in dollars per share)	1
Exercise Prices, Upper Range (in dollars per share)	$ 2
Price Range 3 [Member]
Option Awards Outstanding,Covered Shares Exercised (in shares) | shares	427,500
Option Awards Outstanding, Weighted Average Remaining Contractual Life	7 years 211 days
Option Awards Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 2.13
Option Awards Exercisable, Covered Shares Exercisable (in shares) | shares	230,000
Option Awards Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 2.13
Exercise Prices, Lower Range (in dollars per share)	2.01
Exercise Prices, Upper Range (in dollars per share)	$ 4
Option Awards Outstanding,Covered Shares Exercised (in shares) | shares	2,966,494
Option Awards Outstanding, Weighted Average Remaining Contractual Life
Option Awards Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 1.05
Option Awards Exercisable, Covered Shares Exercisable (in shares) | shares	2,543,941
Option Awards Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.91