Note 12 - Share-based Compensation - Stock-Settled Stock Appreciation Rights Transactions (Details) - Stock Appreciation Rights (SARs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Outstanding SARS (in shares)	325,506	381,566
Outstanding SARS, weighted average exercise price (in dollars per share)	$ 10.26	$ 8.14
Granted SARS (in shares)	43,988	58,108
Granted SARS, weighted average exercise price (in dollars per share)	$ 16.97	$ 16.35
Exercised SARS (in shares)	(222,990)	(114,168)
Exercised SARS, weighted average exercise price (in dollars per share)	$ 6.90	$ 6.27
Granted SARS (in shares)	43,988	58,108
Exercised SARS (in shares)	(222,990)	(114,168)
Outstanding SARS (in shares)	146,504	325,506
Outstanding SARS, weighted average exercise price (in dollars per share)	$ 17.38	$ 10.26