Note 7 - Share-based Compensation - Stock Option Transactions (Details) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 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 28 days		2 years 11 months 12 days
Outstanding, aggregate intrinsic value | $	$ 11,382		$ 714
Granted (in shares) | shares	560,125	[1]
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 9.41	[1]
Exercised (in shares) | shares	(124,722)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 13.13
Lapsed or cancelled (in shares) | shares	(128,549)
Lapsed or cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 17.64
Outstanding, options (in shares) | shares	1,007,985		701,131
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 13.05		$ 16.82
Exercisable, options (in shares) | shares	310,281
Exercisable, weighted average exercise price, options (in dollars per share) | $ / shares	$ 17.48
Exercisable, weighted average remaining life, options (Year)	2 years 6 months 7 days
Exercisable, aggregate intrinsic value, options | $	$ 1,821

[1] The weighted average grant date fair value of stock options granted was $2.36 per share.