Note 12 - Equity Incentive Plans and Employee Benefits - Stock Options by Exercise Prices Range (Details)	12 Months Ended
	Jan. 28, 2017 $ / shares shares
Range of exercise prices, upper limit (in dollars per share)
Number of options outstanding (in shares) | shares	2,665,571
Number of options outstanding, weighted average remaining contractual term (Year)	4 years 175 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 11.25
Number of options exercisable (in shares) | shares	2,131,470
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 12.35
Exercise Price Range One [Member]
Range of exercise prices, lower limit (in dollars per share)	0.92
Range of exercise prices, upper limit (in dollars per share)	$ 4.98
Number of options outstanding (in shares) | shares	297,053
Number of options outstanding, weighted average remaining contractual term (Year)	6 years 346 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 4.60
Number of options exercisable (in shares) | shares	260,579
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 4.55
Exercise Price Range Two [Member]
Range of exercise prices, lower limit (in dollars per share)	5.76
Range of exercise prices, upper limit (in dollars per share)	$ 6.48
Number of options outstanding (in shares) | shares	335,539
Number of options outstanding, weighted average remaining contractual term (Year)	8 years 124 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 6.36
Number of options exercisable (in shares) | shares	95,155
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 6.08
Exercise Price Range Three [Member]
Range of exercise prices, lower limit (in dollars per share)	6.49
Range of exercise prices, upper limit (in dollars per share)	$ 7.30
Number of options outstanding (in shares) | shares	294,240
Number of options outstanding, weighted average remaining contractual term (Year)	7 years 204 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 6.80
Number of options exercisable (in shares) | shares	171,982
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 6.60
Exercise Price Range Four [Member]
Range of exercise prices, lower limit (in dollars per share)	7.44
Range of exercise prices, upper limit (in dollars per share)	$ 10.51
Number of options outstanding (in shares) | shares	209,083
Number of options outstanding, weighted average remaining contractual term (Year)	7 years 105 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 8.39
Number of options exercisable (in shares) | shares	74,098
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 9.28
Exercise Price Range Five [Member]
Range of exercise prices, lower limit (in dollars per share)	10.59
Range of exercise prices, upper limit (in dollars per share)	$ 10.59
Number of options outstanding (in shares) | shares	318,700
Number of options outstanding, weighted average remaining contractual term (Year)	2 years 354 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 10.59
Number of options exercisable (in shares) | shares	318,700
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 10.59
Exercise Price Range Six [Member]
Range of exercise prices, lower limit (in dollars per share)	10.87
Range of exercise prices, upper limit (in dollars per share)	$ 10.87
Number of options outstanding (in shares) | shares	300,600
Number of options outstanding, weighted average remaining contractual term (Year)	1 year 270 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 10.87
Number of options exercisable (in shares) | shares	300,600
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 10.87
Exercise Price Range Seven [Member]
Range of exercise prices, lower limit (in dollars per share)	11.07
Range of exercise prices, upper limit (in dollars per share)	$ 11.09
Number of options outstanding (in shares) | shares	353,934
Number of options outstanding, weighted average remaining contractual term (Year)	2 years 142 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 11.08
Number of options exercisable (in shares) | shares	353,934
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 11.08
Exercise Price Range Eight [Member]
Range of exercise prices, lower limit (in dollars per share)	11.47
Range of exercise prices, upper limit (in dollars per share)	$ 15.25
Number of options outstanding (in shares) | shares	348,422
Number of options outstanding, weighted average remaining contractual term (Year)	2 years 54 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 13.23
Number of options exercisable (in shares) | shares	348,422
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 13.23
Exercise Price Range Nine [Member]
Range of exercise prices, lower limit (in dollars per share)	15.64
Range of exercise prices, upper limit (in dollars per share)	$ 41.58
Number of options outstanding (in shares) | shares	164,000
Number of options outstanding, weighted average remaining contractual term (Year)	1 year 105 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 33.83
Number of options exercisable (in shares) | shares	164,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 33.83
Exercise Price Range Ten [Member]
Range of exercise prices, lower limit (in dollars per share)	45.83
Range of exercise prices, upper limit (in dollars per share)	$ 45.83
Number of options outstanding (in shares) | shares	44,000
Number of options outstanding, weighted average remaining contractual term (Year)	281 days
Number of options outstanding, weighted average exercise price (in dollars per share)	$ 45.83
Number of options exercisable (in shares) | shares	44,000
Number of options exercisable, weighted average exercise price (in dollars per share)	$ 45.83