Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Income Statement [Abstract]
Revenue	$ 65,142	$ 84,193	$ 122,299	$ 155,206
Cost of revenue	21,672	29,345	42,122	54,440
Gross profit	43,470	54,848	80,177	100,766
Operating expenses:
Research and development	23,643	20,840	48,109	37,423
Selling, general and administrative	10,565	9,087	21,458	18,097
Total operating expenses	34,208	29,927	69,567	55,520
Income from operations	9,262	24,921	10,610	45,246
Other income	171	127	198	154
Income before income taxes	9,433	25,048	10,808	45,400
Provision for income taxes	801	1,951	393	3,449
Net income	$ 8,632	$ 23,097	$ 10,415	$ 41,951
Net income per share attributable to ordinary shareholders:
Basic	$ 0.27	$ 0.73	$ 0.32	$ 1.34
Diluted	$ 0.25	$ 0.68	$ 0.31	$ 1.25
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	32,557,398	31,515,446	32,492,723	31,307,236
Diluted	34,175,466	33,904,222	34,063,103	33,688,239