Note 5 - Stock-based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Balance, Shares (in shares)	408,390	420,390	1,031,170	1,031,170
Balance, Weighted-Average Exercise Price (in dollars per share)	$ 23.37	$ 23.80	$ 31.27	$ 31.27
Balance, Weighted-Average Remaining Contractual Life	1 year 146 days	1 year 219 days	1 year 292 days			328 days
Balance, Aggregate Intrinsic Value	$ 1,973	$ 2,026	$ 3,268	$ 3,268
Exercised, Shares (in shares)			(2,110)	(2,110)	(147,350)
Exercised, Weighted-Average Exercise Price (in dollars per share)			$ 23.37
Forfeited, Shares (in shares)		(12,000)	(608,670)
Forfeited, Weighted-Average Exercise Price (in dollars per share)		$ 38.26	$ 36.46
Balance, Shares (in shares)	408,390	408,390	420,390	408,390		1,031,170
Balance, Weighted-Average Exercise Price (in dollars per share)	$ 23.37	$ 23.37	$ 23.80	$ 23.37		$ 31.27
Balance, Aggregate Intrinsic Value	$ 3,026	$ 1,973	$ 2,026	$ 3,026		$ 3,268
Exercisable, Shares (in shares)	408,390			408,390
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 23.37			$ 23.37
Exercisable, Weighted-Average Remaining Contractual Life	1 year 146 days
Exercisable, Aggregate Intrinsic Value	$ 3,026			$ 3,026