Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Income Statement [Abstract]
Revenue	$ 310,297	$ 316,373	$ 218,278
Cost of revenue	105,283	111,029	79,142
Gross profit	205,014	205,344	139,136
Operating expenses:
Research and development	101,205	82,927	57,978
Selling, general and administrative	43,446	37,738	29,297
Total operating expenses	144,651	120,665	87,275
Income from operations	60,363	84,679	51,861
Other income	518	530	175
Income before income taxes	60,881	85,209	52,036
Provision for income taxes	3,071	8,701	1,465
Net income	$ 57,810	$ 76,508	$ 50,571
Net income per share attributable to ordinary shareholders:
Basic	$ 1.77	$ 2.42	$ 1.70
Diluted	$ 1.68	$ 2.27	$ 1.57
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	32,671,221	31,633,936	29,742,653
Diluted	34,327,724	33,755,709	32,278,127