Note 5 - Stock-based Compensation - RSUs Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares shares in Thousands		12 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Restricted stock (in shares)		623	617	503
Restricted stock, weighted average grant date fair value (in dollars per share)		$ 20.56	$ 20.91	$ 16.27
Granted (in shares)		295	307	326
Granted, weighted average grant date fair value (in dollars per share)		$ 30.69	$ 18.54	$ 24.75
Released (in shares)	[1]	(245)	(259)	(192)
Released, weighted average grant date fair value (in dollars per share)	[1]	$ 20.48	$ 18.96	$ 15.58
Forfeited (in shares)		(20)	(42)	(20)
Forfeited, weighted average grant date fair value (in dollars per share)		$ 22.36	$ 20.69	$ 18.93
Restricted stock (in shares)		653	623	617
Restricted stock, weighted average grant date fair value (in dollars per share)		$ 25.10	$ 20.56	$ 20.91

[1] The number of RSUs released includes shares withheld on behalf of employees to satisfy minimum statutory tax withholding requirements. During the fiscal years ended January 31, 2018, 2017 and 2016, the Company withheld 74,000 shares, 75,000 shares and 52,000 shares, respectively, for payment of these taxes. The value of the withheld shares for the fiscal years ended January 31, 2018, 2017 and 2016 were $2.4 million, $1.5 million and $1.4 million, respectively.