Note 7 - Share-based Compensation - Stock Option Transactions (Details) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares		Dec. 31, 2019 USD ($) $ / shares shares
Outstanding, options (in shares) | shares	701,131
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 16.82
Outstanding, weighted average remaining life (Year)	3 years 10 months 2 days		2 years 11 months 12 days
Outstanding, aggregate intrinsic value | $	$ 3,405		$ 714
Granted (in shares) | shares	528,900	[1]
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 8.70	[1]
Exercised (in shares) | shares	(14,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 4.71
Lapsed or cancelled (in shares) | shares	(111,668)
Lapsed or cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 17.81
Outstanding, options (in shares) | shares	1,104,363		701,131
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 12.98		$ 16.82
Exercisable, options (in shares) | shares	400,863
Exercisable, weighted average exercise price, options (in dollars per share) | $ / shares	$ 16.46
Exercisable, weighted average remaining life, options (Year)	2 years 3 months 14 days
Exercisable, aggregate intrinsic value, options | $	$ 579

[1] The weighted average grant date fair value of stock options granted was $2.04 per share.