Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (165,724)	$ (202,151)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	45,525	35,978
Stock-based compensation expense	107,920	79,129
Other	879	1,051
Changes in operating assets and liabilities:
Accounts receivable, net	(33,630)	(38,186)
Inventory	(14,314)	(189)
Deferred commissions	(7,629)	1,844
Prepaid expenses and other current assets	(112)	39
Accounts payable	11,808	3,639
Accrued compensation and other liabilities	14,629	6,786
Deferred revenue	54,404	60,180
Net cash provided by (used in) operating activities	13,756	(51,880)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(44,351)	(64,602)
Purchase of intangible assets	0	(1,000)
Purchases of marketable securities	(151,998)	(483,558)
Sales of marketable securities	46,067	79,815
Maturities of marketable securities	99,021	38,213
Net increase in restricted cash	(2,029)	(5,600)
Net cash used in investing activities	(53,290)	(436,732)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options	15,761	10,725
Proceeds from issuance of common stock under employee stock purchase plan	22,137	25,606
Net cash provided by financing activities	37,898	36,331
Net decrease in cash and cash equivalents	(1,636)	(452,281)
Cash and cash equivalents, beginning of period	183,675	604,742
Cash and cash equivalents, end of period	182,039	152,461
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	2,410	2,510
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid	9,831	5,956
Vesting of early exercised stock options	$ 794	$ 794