Note 4 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) shares in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2020	Dec. 31, 2019
Outstanding (in shares)		584
Outstanding, weighted average exercise price (in dollars per share)		$ 14.94
Outstanding, weighted average remaining contractual life (Year)		7 years 146 days	7 years 328 days
Outstanding, aggregate intrinsic value	[1]
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)		(3)
Forfeited, weighted average exercise price (in dollars per share)		$ 4.37
Outstanding (in shares)		581	584
Outstanding, weighted average exercise price (in dollars per share)		$ 14.93	$ 14.94
Exercisable (in shares)		386
Exercisable, weighted average exercise price (in dollars per share)		$ 15.62
Exercisable, weighted average remaining contractual life (Year)		6 years 328 days
Exercisable, aggregate intrinsic value	[1]

[1] Stock options had no aggregate intrinsic value as of December 31, 2019 and June 30, 2020. Intrinsic value is calculated based on the amount by which the closing market value of the Company's stock exceeded the exercise price of the underlying options, multiplied by the number of shares.