Note 6 - Stock-based Compensation - RSUs Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares shares in Thousands		12 Months Ended
		Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Restricted stock (in shares)		663	653	623
Restricted stock, weighted average grant date fair value (in dollars per share)		$ 36.64	$ 25.10	$ 20.56
Granted (in shares)		281	300	295
Granted, weighted average grant date fair value (in dollars per share)		$ 40.43	$ 51.70	$ 30.69
Released (in shares)	[1]	(267)	(263)	(245)
Released, weighted average grant date fair value (in dollars per share)	[1]	$ 32.71	$ 25.80	$ 20.48
Forfeited (in shares)		(50)	(27)	(20)
Forfeited, weighted average grant date fair value (in dollars per share)		$ 38.51	$ 30.63	$ 22.36
Restricted stock (in shares)		627	663	653
Restricted stock, weighted average grant date fair value (in dollars per share)		$ 39.86	$ 36.64	$ 25.10

[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, 2020, 2019 and 2018, the Company withheld 82,000 shares, 81,000 shares and 74,000 shares, respectively, for payment of these taxes. The value of the withheld shares for the fiscal years ended January 31, 2020, 2019 and 2018 were $3.5 million, $4.3 million and $2.4 million, respectively.