Note 7 - Stock-based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding, shares (in shares)	5	14	90
Outstanding, Weighted average exercise price (in dollars per share)	$ 13.89	$ 15.88	$ 17.50
Outstanding, Weighted average remaining contractual term (Year)		146 days	1 year	1 year 109 days
Outstanding, Aggregate intrinsic value		$ 465	$ 921	$ 4,134
Exercised, shares (in shares)	(5)	(9)	(76)
Exercised, Weighted average exercise price (in dollars per share)	$ 13.89	$ 16.79	$ 17.80
Outstanding, shares (in shares)		5	14	90
Outstanding, Weighted average exercise price (in dollars per share)		$ 13.89	$ 15.88	$ 17.50