Note 4 - Stockholders' Equity - Stock Options Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) $ / shares shares
Outstanding (in shares)		1,045,000
Outstanding, weighted average exercise price (in dollars per share) | $ / shares		$ 9.65
Granted (in shares)	0	10,000
Exercised (in shares)		(59,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares		$ 7.069
Canceled (in shares)		(6,000)
Canceled, weighted average exercise price (in dollars per share) | $ / shares		$ 14.02
Expired (in shares)		(4,000)
Expired, weighted average exercise price (in dollars per share) | $ / shares		$ 16.22
Outstanding (in shares)	986,000	986,000
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 9.80	$ 9.80
Outstanding, weighted average remaining term (Year)		4 years 186 days
Outstanding, intrinsic value | $	$ 3,404	$ 3,404
Vested and expected to vest, June 30, 2018 (in shares)	977,000	977,000
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 9.71	$ 9.71
Vested and expected to vest, weighted average remaining term (Year)		4 years 160 days
Vested and expected to vest, intrinsic value | $	$ 3,403	$ 3,403
Exercisable, June 30, 2018 (in shares)	808,000	808,000
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 8.50	$ 8.50
Exercisable, weighted average remaining term (Year)		3 years 204 days
Exercisable, intrinsic value | $	$ 3,380	$ 3,380