Note 4 - Stockholders' Equity - Stock Options Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares
Outstanding (in shares) | shares		1,045,000
Outstanding, weighted average exercise price (in dollars per share) | $ / shares		$ 9.65
Granted (in shares) | shares	87,000	98,000
Granted, weighted average exercise price (in dollars per share) | $ / shares		$ 10.71
Exercised (in shares) | shares		(68,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares		$ 6.88
Canceled or expired (in shares) | shares		(30,000)
Canceled or expired, weighted average exercise price (in dollars per share) | $ / shares		$ 13.84
Outstanding (in shares) | shares	1,045,000	1,045,000
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 9.81	$ 9.81
Outstanding, weighted average remaining term (Year)		4 years 233 days
Outstanding, intrinsic value | $	$ 1,422	$ 1,422
Vested and expected to vest (in shares) | shares	1,039,000	1,039,000
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 9.77	$ 9.77
Vested and expected to vest, weighted average remaining term (Year)		4 years 215 days
Vested and expected to vest, intrinsic value | $	$ 1,422	$ 1,422
Exercisable (in shares) | shares	806,000	806,000
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 8.60	$ 8.60
Exercisable, weighted average remaining term (Year)		3 years 113 days
Exercisable, intrinsic value | $	$ 1,422	$ 1,422