Note 15 - Stock-based Compensation - Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2016 $ / shares shares
Number outstanding (in shares) | shares	587,961
Number exercisable (in shares) | shares	385,372
Range 1 [Member]
Exercise price range, lower range (in dollars per share)	$ 7.99
Exercise price range, upper range (in dollars per share)	$ 8.93
Number outstanding (in shares) | shares	35,040
Weighted average remaining contractual life (Year)	3 years 306 days
Weighted average exercise price options outstanding (in dollars per share)	$ 8.18
Number exercisable (in shares) | shares	35,040
Weighted average exercise price options exercisable (in dollars per share)	$ 8.18
Range 2 [Member]
Exercise price range, lower range (in dollars per share)	9
Exercise price range, upper range (in dollars per share)	$ 9.30
Number outstanding (in shares) | shares	160,707
Weighted average remaining contractual life (Year)	3 years 299 days
Weighted average exercise price options outstanding (in dollars per share)	$ 9.22
Number exercisable (in shares) | shares	147,200
Weighted average exercise price options exercisable (in dollars per share)	$ 9.22
Range 3 [Member]
Exercise price range, lower range (in dollars per share)	15
Exercise price range, upper range (in dollars per share)	$ 16.85
Number outstanding (in shares) | shares	168,164
Weighted average remaining contractual life (Year)	3 years 233 days
Weighted average exercise price options outstanding (in dollars per share)	$ 15.69
Number exercisable (in shares) | shares	147,291
Weighted average exercise price options exercisable (in dollars per share)	$ 15.69
Range 4 [Member]
Exercise price range, lower range (in dollars per share)	17.10
Exercise price range, upper range (in dollars per share)	$ 18
Number outstanding (in shares) | shares	145,551
Weighted average remaining contractual life (Year)	7 years 204 days
Weighted average exercise price options outstanding (in dollars per share)	$ 17.25
Number exercisable (in shares) | shares	55,341
Weighted average exercise price options exercisable (in dollars per share)	$ 17.25
Range 5 [Member]
Exercise price range, lower range (in dollars per share)	21.71
Exercise price range, upper range (in dollars per share)	$ 31.53
Number outstanding (in shares) | shares	78,499
Weighted average remaining contractual life (Year)	9 years 32 days
Weighted average exercise price options outstanding (in dollars per share)	$ 21.71
Number exercisable (in shares) | shares	500
Weighted average exercise price options exercisable (in dollars per share)	$ 21.71