Note 17 - Stock-based Compensation - Stock Option and SARs Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of SARs outstanding (in shares)	731
Options and SARs (in shares)	(731)
Award Vested and Exercisable [Member]
Number of SARs outstanding (in shares)	492	490	475
Exercise price (in dollars per share)	$ 17.69	$ 16.46	$ 15.72
Aggregate intrinsic value	$ 7,505	$ 10,408	$ 14,820
Weighted average fair value (in dollars per share)	$ 3.21	$ 3.16	$ 3.16
Weighted average remaining contractual life (Year)	3 years 292 days	4 years	4 years 109 days
Options and SARs (in shares)	(492)	(490)	(475)
Award Vested and Exercisable [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 14.02	$ 14.02	$ 14.02
Award Vested and Exercisable [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 40	$ 33.08	$ 24.56
Award Unvested [Member]
Number of SARs outstanding (in shares)	239	214	260
Exercise price (in dollars per share)	$ 32.15	$ 26.46	$ 21.53
Aggregate intrinsic value	$ 917	$ 2,515	$ 6,623
Weighted average fair value (in dollars per share)	$ 5.09	$ 4.17	$ 3.43
Weighted average remaining contractual life (Year)	8 years	7 years 255 days	7 years 292 days
Options and SARs (in shares)	(239)	(214)	(260)
Award Unvested [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 19.37	$ 15.26	$ 15.24
Award Unvested [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 40	$ 40	$ 33.08
Award Outstanding [Member]
Number of SARs outstanding (in shares)	731	704	735
Exercise price (in dollars per share)	$ 22.42	$ 19.51	$ 17.78
Aggregate intrinsic value	$ 8,422	$ 12,923	$ 21,443
Weighted average fair value (in dollars per share)	$ 3.82	$ 3.47	$ 3.26
Weighted average remaining contractual life (Year)	5 years 73 days	5 years 36 days	5 years 182 days
Options and SARs (in shares)	(731)	(704)	(735)
Award Outstanding [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 14.02	$ 14.02	$ 14.02
Award Outstanding [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 40	$ 40	$ 33.08
Award Granted [Member]
Number of SARs outstanding (in shares)	100	46
Exercise price (in dollars per share)	$ 37.75	$ 40
Weighted average fair value (in dollars per share)	$ 6.07	$ 6.34
Options and SARs (in shares)	(100)	(46)
Award Granted [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 35.90	$ 40
Award Granted [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 39.32	$ 40
Award Exercised [Member]
Number of SARs outstanding (in shares)	73	77
Exercise price (in dollars per share)	$ 15.32	$ 15.41
Aggregate intrinsic value	$ 1,654	$ 1,855
Weighted average fair value (in dollars per share)	$ 3.43	$ 3.18
Weighted average remaining contractual life (Year)
Options and SARs (in shares)	(73)	(77)
Award Exercised [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 14.02	$ 14.02
Award Exercised [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 19.37	$ 17.89
Award Forfeited [Member]
Number of SARs outstanding (in shares)
Exercise price (in dollars per share)
Aggregate intrinsic value
Weighted average fair value (in dollars per share)
Weighted average remaining contractual life (Year)
Options and SARs (in shares)
Award Forfeited [Member] | Minimum [Member]
Exercise price (in dollars per share)
Award Forfeited [Member] | Maximum [Member]
Exercise price (in dollars per share)
Award Vested [Member]
Number of SARs outstanding (in shares)	75
Exercise price (in dollars per share)	$ 23.38
Aggregate intrinsic value	$ 776
Weighted average fair value (in dollars per share)	$ 3.77
Weighted average remaining contractual life (Year)
Options and SARs (in shares)	(75)
Award Vested [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 15.26
Award Vested [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 40