Net income (loss) per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Numerator (basic and diluted):
Net income (loss)	$ 1,789	$ (21,334)	$ 3,467	$ 39,854
Denominator (basic):
Weighted-average common shares outstanding (in shares)	76,701	70,524	73,358	65,727
Denominator (diluted):
Weighted-average common shares outstanding (in shares)	76,701	70,524	73,358	65,727
Weighted-average dilutive effect of stock options and restricted stock units (in shares)	1,144	0	1,307	1,423
Diluted weighted-average common shares outstanding (in shares)	77,845	70,524	74,665	67,150
Net income (loss) per share:
Basic (in usd per share)	$ 0.02	$ (0.30)	$ 0.05	$ 0.61
Diluted (in usd per share)	$ 0.02	$ (0.30)	$ 0.05	$ 0.59
Antidilutive securities excluded from computation of earnings per share (in shares)	1,000	3,200	600	300