Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Income Statement [Abstract]
Revenue	$ 316,373	$ 218,278	$ 157,608
Cost of revenue	111,029	79,142	57,761
Gross profit	205,344	139,136	99,847
Operating expenses:
Research and development	82,927	57,978	48,777
Selling, general and administrative	37,738	29,297	23,153
Total operating expenses	120,665	87,275	71,930
Income from operations	84,679	51,861	27,917
Other income (loss), net	530	175	(22)
Income before income taxes	85,209	52,036	27,895
Provision for income taxes	8,701	1,465	2,241
Net income	$ 76,508	$ 50,571	$ 25,654
Net income per share attributable to ordinary shareholders:
Basic	$ 2.42	$ 1.70	$ 0.93
Diluted	$ 2.27	$ 1.57	$ 0.85
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	31,633,936	29,742,653	27,680,778
Diluted	33,755,709	32,278,127	30,172,563