Note 3 - Stock-Based Compensation - Stock Option Activity (Details) - $ / shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Options outstanding (in shares)	1,065,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 2.19
Granted to employees and non-employee directors (in shares)	0	810,000
Granted to employees and non-employee directors, weighted average exercise price (in dollars per share)
Exercised (in shares)	(40,000)
Exercised, weighted average exercise price (in dollars per share)	$ 1.53
Canceled/expired/forfeited (in shares)	(20,000)
Canceled/expired/forfeited, weighted average exercise price (in dollars per share)	$ 1.58
Options outstanding (in shares)	1,005,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 2.09
Options exercisable (in shares)	357,300
Options exercisable, weighted average exercise price (in dollars per share)	$ 1.97