Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (245,066)	$ (213,752)	$ (183,231)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	50,203	32,254	15,392
Stock-based compensation expense	116,668	58,225	25,399
Contribution of common stock to the Pure Good Foundation	0	11,900	0
Other	1,584	(1,093)	277
Changes in operating assets and liabilities:
Accounts receivable, net	(44,049)	(67,292)	(44,197)
Inventory	(3,776)	1,481	(13,713)
Deferred commissions	(740)	(13,021)	(9,838)
Prepaid expenses and other current assets	(6,133)	(8,704)	(6,550)
Accounts payable	10,644	24,901	3,474
Accrued compensation and other liabilities	19,381	24,710	12,450
Deferred revenue	86,922	142,535	56,842
Net cash used in operating activities	(14,362)	(7,856)	(143,695)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(76,773)	(39,355)	(42,227)
Purchase of intangible assets	(1,000)	0	(9,125)
Purchases of marketable securities	(526,717)	0	0
Sales of marketable securities	114,354	0	0
Maturities of marketable securities	48,513	0	0
Net increase in restricted cash	(5,600)	(2,485)	(1,613)
Net cash used in investing activities	(447,223)	(41,840)	(52,965)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from initial public offering, net of issuance costs	0	459,425	0
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	0	280,970
Net proceeds from exercise of stock options, including proceeds from repayment of promissory notes	14,912	6,008	7,665
Proceeds from issuance of common stock under employee stock purchase plan	25,606	0	0
Repurchase of common stock in connection with tender offer	0	0	(30,120)
Payments of deferred offering costs	0	(3,702)	(33)
Net cash provided by financing activities	40,518	461,731	258,482
Net increase in cash and cash equivalents	(421,067)	412,035	61,822
Cash and cash equivalents, beginning of period	604,742	192,707	130,885
Cash and cash equivalents, end of period	183,675	604,742	192,707
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	2,866	1,118	429
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Conversion of convertible preferred stock to common stock upon initial public offering	0	543,940	0
Property and equipment purchased but not yet paid	7,414	6,212	1,323
Vesting of early exercised stock options	3,399	1,725	1,162
Cashless exercise of stock options during tender offer	0	0	2,057
Unpaid deferred offering costs	$ 0	$ 546	$ 55