Note 6 - Share-based Compensation - Stock-settled Stock Appreciation Rights Transactions (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2019	Dec. 31, 2018
Outstanding SARS (in shares)		182,894
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 18.99
Outstanding SARS, weighted average remaining life (Year)		2 years 208 days	2 years 222 days
Outstanding SARS, aggregate intrinsic value		$ 40	$ 89
Granted SARs (in shares)	[1]	42,841
Granted SARS, weighted average exercise price (in dollars per share)	[1]	$ 17.77
Exercised SARs (in shares)
Exercised SARS, weighted average exercise price (in dollars per share)
Cancelled SARs (in shares)		(16,162)
Cancelled SARS, weighted average exercise price (in dollars per share)		$ 20.01
Outstanding SARS (in shares)		209,573	182,894
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 18.66	$ 18.99
Exercisable SARs (in shares)		168,478
Exercisable SARs, weighted average exercise price (in dollars per share)		$ 18.88
Exercisable SARs, weighted average remaining life (Year)		2 years 25 days
Exercisable SARs, aggregate intrinsic value		$ 40

[1] The weighted average grant date fair value of SARs granted was $3.97 per share.