Note 7 - Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding, shares (in shares)	14	90	590
Outstanding, Weighted average exercise price (in dollars per share)	$ 15.88	$ 17.50	$ 15.80
Outstanding, Weighted average remaining contractual term (Year)	146 days	1 year	1 year 109 days	1 year 73 days
Outstanding, Aggregate intrinsic value	$ 465	$ 921	$ 4,134	$ 20,039
Exercised, shares (in shares)	(9)	(76)	(498)
Exercised, Weighted average exercise price (in dollars per share)	$ 16.79	$ 17.80	$ 15.55
Forfeited and expired, shares (in shares)			(2)
Forfeited and expired, Weighted average exercise price (in dollars per share)			$ 6.10
Outstanding, shares (in shares)	5	14	90	590
Outstanding, Weighted average exercise price (in dollars per share)	$ 13.89	$ 15.88	$ 17.50	$ 15.80
Options exercisable, shares (in shares)	5
Options exercisable, Weighted average exercise price (in dollars per share)	$ 13.89
Options exercisable, Weighted average remaining contractual term (Year)	146 days
Options exercisable, Aggregate intrinsic value	$ 465