Note 10 - Common Stock and Stock-based Compensation Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2020		Dec. 31, 2019
Outstanding, Number of shares (in shares)	[1]	642,253
Outstanding, Weighted average exercise price (in dollars per share)		$ 20.14
Outstanding, Weighted average remaining contractual term (Year)		3 years 146 days	[2]	3 years 182 days
Outstanding, Aggregated intrinsic value		$ 2,524	[2]	$ 4,718
Granted, Number of shares (in shares)	[1]
Exercised, Number of shares (in shares)	[1]	(161,001)
Exercised, Weighted average exercise price (in dollars per share)		$ 17.55
Forfeited or expired, Number of shares (in shares)	[1]
Forfeited or expired, Weighted average exercise price (in dollars per share)
Outstanding, Number of shares (in shares)	[1]	481,252	[2]	642,253
Outstanding, Weighted average exercise price (in dollars per share)		$ 21.01	[2]	$ 20.14
Exercisable, Number of shares (in shares)	[1],[3]	455,252
Exercisable, Weighted average exercise price (in dollars per share)	[3]	$ 20.59
Exercisable, Weighted average remaining contractual term (Year)	[3]	3 years 73 days
Exercisable, Aggregated intrinsic value	[3]	$ 2,524

[1] The SAR units are convertible for a maximum number of shares of the Company's common stock equal to 75% of the SAR units subject to the grant.

[2] Due to the ceiling imposed on the SAR grants, the outstanding amount equals a maximum of 452,564 shares of the Company’s common stock issuable upon exercise.

[3] Due to the ceiling imposed on the SAR grants, the exercisable amount equals a maximum of 426,564 shares of the Company’s common stock issuable upon exercise.