Note 13 - Stock-based Compensation - Stock Option and SARs Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Award Vested and Exercisable [Member]
Options and SARs (in shares)	519	475	656
Exercise price (in dollars per share)	$ 16.39	$ 15.72	$ 15.75
Aggregate intrinsic value	$ 11,218	$ 14,820	$ 6,191
Weighted average fair value (in dollars per share)	$ 3.15	$ 3.16	$ 3.39
Weighted average remaining contractual life (Year)	4 years 109 days	4 years 109 days	3 years 255 days
Options and SARs (in shares)	(519)	(475)	(656)
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)	$ 25.76	$ 24.56	$ 19.44
Award Unvested [Member]
Options and SARs (in shares)	215	260	266
Exercise price (in dollars per share)	$ 26.45	$ 21.53	$ 18.66
Aggregate intrinsic value	$ 2,567	$ 6,623	$ 1,733
Weighted average fair value (in dollars per share)	$ 4.17	$ 3.43	$ 3.29
Weighted average remaining contractual life (Year)	7 years 328 days	7 years 292 days	7 years 255 days
Options and SARs (in shares)	(215)	(260)	(266)
Award Unvested [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 15.24	$ 15.24	$ 15.24
Award Unvested [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 40	$ 33.08	$ 24.55
Award Outstanding [Member]
Options and SARs (in shares)	734	735	922
Exercise price (in dollars per share)	$ 19.17	$ 17.78	$ 16.59
Aggregate intrinsic value	$ 13,785	$ 21,443	$ 7,924
Weighted average fair value (in dollars per share)	$ 3.45	$ 3.26	$ 3.36
Weighted average remaining contractual life (Year)	5 years 109 days	5 years 182 days	4 years 292 days
Options and SARs (in shares)	(734)	(735)	(922)
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	$ 33.08	$ 24.55
Award Granted [Member]
Options and SARs (in shares)		46	88
Exercise price (in dollars per share)		$ 40	$ 25.84
Aggregate intrinsic value			$ 1,866
Weighted average fair value (in dollars per share)		$ 6.34	$ 3.56
Weighted average remaining contractual life (Year)
Options and SARs (in shares)		(46)	(88)
Award Granted [Member] | Minimum [Member]
Exercise price (in dollars per share)		$ 40	$ 25.76
Award Granted [Member] | Maximum [Member]
Exercise price (in dollars per share)		$ 40	$ 33.08
Award Exercised [Member]
Options and SARs (in shares)		47	272
Exercise price (in dollars per share)		$ 15.52	$ 16.38
Aggregate intrinsic value		$ 1,168	$ 4,155
Weighted average fair value (in dollars per share)		$ 3.27	$ 3.73
Weighted average remaining contractual life (Year)
Options and SARs (in shares)		(47)	(272)
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)		$ 17.89	$ 17.89
Award Forfeited [Member]
Options and SARs (in shares)			3
Exercise price (in dollars per share)			$ 15.18
Aggregate intrinsic value			$ 60
Weighted average fair value (in dollars per share)			$ 2.94
Weighted average remaining contractual life (Year)
Options and SARs (in shares)			(3)
Award Forfeited [Member] | Minimum [Member]
Exercise price (in dollars per share)			$ 14.02
Award Forfeited [Member] | Maximum [Member]
Exercise price (in dollars per share)			$ 15.84
Award Vested [Member]
Options and SARs (in shares)	92
Exercise price (in dollars per share)	$ 19.34
Aggregate intrinsic value	$ 1,723
Weighted average fair value (in dollars per share)	$ 3.18
Weighted average remaining contractual life (Year)
Options and SARs (in shares)	(92)
Award Vested [Member] | Minimum [Member]
Exercise price (in dollars per share)	$ 15.24
Award Vested [Member] | Maximum [Member]
Exercise price (in dollars per share)	$ 25.76