Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Income Statement [Abstract]
Revenue	$ 100,490	$ 93,200	$ 222,789	$ 248,406
Cost of revenue	34,167	31,938	76,289	86,378
Gross profit	66,323	61,262	146,500	162,028
Operating expenses:
Research and development	25,967	22,062	74,076	59,485
Selling, general and administrative	10,686	8,873	32,144	26,970
Total operating expenses	36,653	30,935	106,220	86,455
Income from operations	29,670	30,327	40,280	75,573
Other income	132	169	330	323
Income before income taxes	29,802	30,496	40,610	75,896
Provision for income taxes	757	1,035	1,150	4,484
Net income	$ 29,045	$ 29,461	$ 39,460	$ 71,412
Net income per share attributable to ordinary shareholders:
Basic	$ 0.89	$ 0.93	$ 1.21	$ 2.27
Diluted	$ 0.84	$ 0.87	$ 1.15	$ 2.12
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	32,670,784	31,815,588	32,552,077	31,476,668
Diluted	34,599,992	33,899,202	34,242,065	33,758,541