Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Income Statement [Abstract]
Revenue	$ 228,732	$ 227,768	$ 295,402
Cost of revenue	96,023	89,624	107,669
Gross profit	132,709	138,144	187,733
Operating expenses:
Research and development	129,724	128,084	115,510
Selling, general and administrative	52,634	50,480	47,792
Total operating expenses	182,358	178,564	163,302
Income (loss) from operations	(49,649)	(40,420)	24,431
Other income, net	8,021	5,868	1,298
Income (loss) before income taxes	(41,628)	(34,552)	25,729
Provision (benefit) for income taxes	3,164	(4,105)	6,877
Net income (loss)	$ (44,792)	$ (30,447)	$ 18,852
Net income (loss) per share attributable to ordinary shareholders:
Basic	$ (1.35)	$ (0.93)	$ 0.57
Diluted	$ (1.35)	$ (0.93)	$ 0.55
Weighted-average shares used to compute net income (loss) per share attributable to ordinary shareholders:
Basic	33,083,562	32,713,606	33,224,803
Diluted	33,083,562	32,713,606	34,583,150