Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Series E Convertible Preferred Stock	Series F Convertible Preferred Stock	Series F-1 Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Stockholders' equity balance at Jan. 31, 2013	$ (39,150)				$ 3	$ 3,317	$ (42,470)
Stockholders' equity balance (in shares) at Jan. 31, 2013					27,438,000
Temporary equity balance at Jan. 31, 2013	$ 95,137
Temporary equity balance (in shares) at Jan. 31, 2013	79,409,000
Issuance of convertible preferred stock		$ 167,833
Issuance of convertible preferred stock (in shares)		24,697,000
Issuance of common stock upon exercise of stock options	$ 336				$ 0	336	0
Issuance of common stock upon exercise of stock options (in shares)					4,047,000
Repurchase of common stock in connection with tender offer (Note 9)	(7,202)				$ 0	0	(7,202)
Repurchase of common stock in connection with tender offer (Note 9) (in shares)					(3,046,000)
Stock-based compensation expense	8,298				$ 0	8,298	0
Vesting of early exercised stock options	192				0	192	0
Net loss	(78,561)				0	0	(78,561)
Stockholders' equity balance at Jan. 31, 2014	(116,087)				$ 3	12,143	(128,233)
Stockholders' equity balance (in shares) at Jan. 31, 2014					28,439,000
Temporary equity balance at Jan. 31, 2014	$ 262,970
Temporary equity balance (in shares) at Jan. 31, 2014	104,106,000
Issuance of convertible preferred stock		$ 450	$ 220,803	$ 59,717
Issuance of convertible preferred stock (in shares)		65,000	14,308,000	3,802,000
Issuance of common stock upon exercise of stock options, including stock options exercised via promissory notes (Note 9)	$ 3,047				$ 2	3,045	0
Issuance of common stock upon exercise of stock options, including stock options exercised via promissory notes (Note 9) (in shares)					11,879,000
Repurchase of common stock in connection with tender offer (Note 9)	(30,120)				$ (1)	0	(30,119)
Repurchase of common stock in connection with tender offer (Note 9) (in shares)					(3,803,000)
Repurchase of common stock from early exercised stock options	0				$ 0	0	0
Repurchase of common stock from early exercised stock options (in shares)					(50,000)
Stock-based compensation expense	25,399				$ 0	25,399	0
Vesting of early exercised stock options	1,162				0	1,162	0
Net loss	(183,231)				0	0	(183,231)
Stockholders' equity balance at Jan. 31, 2015	(299,830)				$ 4	41,749	(341,583)
Stockholders' equity balance (in shares) at Jan. 31, 2015					36,465,000
Temporary equity balance at Jan. 31, 2015	$ 543,940	$ 168,283	$ 220,803	$ 59,717
Temporary equity balance (in shares) at Jan. 31, 2015	122,280,679	24,761,984	14,307,603	3,801,746
Conversion of convertible preferred stock to common stock upon initial public offering	$ 543,940				$ 12	543,928	0
Conversion of convertible preferred stock to common stock upon initial public offering (in shares)					122,281,000
Temporary equity, conversion of convertible preferred stock to common stock upon initial public offering	$ (543,940)
Temporary equity, conversion of convertible preferred stock to common stock upon initial public offering (in shares)	(122,281,000)
Issuance of common stock upon initial public offering, net of offering costs of $4,539	$ 455,138				$ 3	455,135	0
Issuance of common stock upon initial public offering (in shares)					28,750,000
Issuance of common stock to Pure Good Foundation	$ 11,900					11,900
Issuance of common stock to Pure Good Foundation (in shares)					700,000
Issuance of common stock upon exercise of stock options (in shares)	2,313,598
Stock-based compensation expense	$ 58,225				$ 0	58,225	0
Vesting of early exercised stock options	1,725				0	1,725	0
Net loss	(213,752)				0	0	(213,752)
Stockholders' equity balance at Jan. 31, 2016	563,354				$ 19	1,118,670	(555,335)
Stockholders' equity balance (in shares) at Jan. 31, 2016					190,509,000
Temporary equity balance at Jan. 31, 2016	$ 0
Temporary equity balance (in shares) at Jan. 31, 2016	0
Issuance of common stock upon exercise of stock options, net of repurchases	$ 6,008				$ 0	$ 6,008	$ 0
Issuance of common stock upon, net of repurchases exercise of stock options (in shares)					2,313,000