Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Income Statement [Abstract]
Revenue	$ 56,410	$ 62,474	$ 103,598	$ 119,412
Cost of revenue	23,973	24,461	43,308	46,507
Gross profit	32,437	38,013	60,290	72,905
Operating expenses:
Research and development	30,420	32,129	63,437	63,793
Selling, general and administrative	12,425	12,566	25,502	25,744
Total operating expenses	42,845	44,695	88,939	89,537
Loss from operations	(10,408)	(6,682)	(28,649)	(16,632)
Other income, net	2,195	732	4,391	1,524
Loss before income taxes	(8,213)	(5,950)	(24,258)	(15,108)
Provision for income taxes	1,978	927	3,244	1,775
Net loss	$ (10,191)	$ (6,877)	$ (27,502)	$ (16,883)
Net loss per share attributable to ordinary shareholders:
Basic	$ (0.31)	$ (0.21)	$ (0.84)	$ (0.51)
Diluted	$ (0.31)	$ (0.21)	$ (0.84)	$ (0.51)
Weighted-average shares used to compute net loss per share attributable to ordinary shareholders:
Basic	32,860,974	33,219,152	32,676,509	33,276,976
Diluted	32,860,974	33,219,152	32,676,509	33,276,976