Note 5 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Outstanding (in shares)		398
Outstanding, weighted average exercise price (in dollars per share)		$ 17.09
Outstanding, weighted average remaining contractual life (Year)		7 years 328 days	8 years 73 days
Outstanding, aggregate intrinsic value	[1]	$ 203	$ 493
Granted (in shares)
Granted, weighted average exercise price (in dollars per share)
Exercised (in shares)
Exercised, weighted average exercise price (in dollars per share)
Forfeited (in shares)
Forfeited, weighted average exercise price (in dollars per share)
Outstanding (in shares)		398	398
Outstanding, weighted average exercise price (in dollars per share)		$ 17.09	$ 17.09
Exercisable (in shares)		143
Exercisable, weighted average exercise price (in dollars per share)		$ 14.51
Exercisable, weighted average remaining contractual life (Year)		7 years 109 days
Exercisable, aggregate intrinsic value	[1]	$ 123

[1] The aggregate intrinsic value on this table was calculated based on the amount, if any, by which the closing market value of the Company's stock on March 31, 2019 ($14.03) exceeded the exercise price of the underlying options, multiplied by the number of shares subject to each option.