CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Income Statement [Abstract]
Revenue	$ 129,304	$ 102,811	$ 369,467	$ 288,679
Cost of revenue	34,471	27,115	99,972	82,576
Gross profit	94,833	75,696	269,495	206,103
Operating expenses:
Research and development	34,812	29,652	102,388	84,824
Sales and marketing	81,670	66,796	225,604	186,454
General and administrative	20,910	16,999	63,037	49,087
Total operating expenses	137,392	113,447	391,029	320,365
Loss from operations	(42,559)	(37,751)	(121,534)	(114,262)
Interest expense, net	(287)	(222)	(802)	(587)
Other income (expense), net	277	(22)	560	609
Loss before provision for income taxes	(42,569)	(37,995)	(121,776)	(114,240)
Provision for income taxes	355	238	519	670
Net loss	$ (42,924)	$ (38,233)	$ (122,295)	$ (114,910)
Net loss per common share, basic and diluted	$ (0.32)	$ (0.30)	$ (0.92)	$ (0.91)
Weighted-average shares used to compute net loss per share, basic and diluted	134,636	128,275	133,044	126,712