CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Income Statement [Abstract]
Revenue	$ 506,142	$ 398,605	$ 302,704
Cost of revenue	135,248	112,130	87,100
Gross profit	370,894	286,475	215,604
Operating expenses:
Research and development	136,791	115,928	102,500
Sales and marketing	303,319	253,020	242,184
General and administrative	84,805	68,182	71,923
Total operating expenses	524,915	437,130	416,607
Loss from operations	(154,021)	(150,655)	(201,003)
Interest expense, net	(1,013)	(896)	(1,157)
Other income (expense), net	789	678	(98)
Loss before provision for income taxes	(154,245)	(150,873)	(202,258)
Provision for income taxes	715	914	690
Net loss attributable to common stockholders	$ (154,960)	$ (151,787)	$ (202,948)
Net loss per common share, basic and diluted	$ (1.16)	$ (1.19)	$ (1.67)
Weighted-average shares used to compute net loss per share, basic and diluted	133,932	127,469	121,240