Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (124,075)	$ (123,338)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	30,000	22,336
Stock-based compensation expense	69,057	50,894
Other	797	494
Changes in operating assets and liabilities:
Accounts receivable, net	25	6,589
Inventory	(10,487)	(2,392)
Deferred commissions	(4,607)	1,887
Prepaid expenses and other current assets	(186)	(809)
Accounts payable	201	(10,007)
Accrued compensation and other liabilities	310	8,687
Deferred revenue	24,473	41,102
Net cash used in operating activities	(14,492)	(4,557)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(30,100)	(46,118)
Purchase of intangible assets	0	(1,000)
Purchases of marketable securities	(95,358)	(427,968)
Sales of marketable securities	33,529	59,071
Maturities of marketable securities	73,681	5,800
Net increase in restricted cash	0	(5,600)
Net cash used in investing activities	(18,248)	(415,815)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options	6,793	6,369
Proceeds from issuance of common stock under employee stock purchase plan	14,166	15,079
Net cash provided by financing activities	20,959	21,448
Net decrease in cash and cash equivalents	(11,781)	(398,924)
Cash and cash equivalents, beginning of period	183,675	604,742
Cash and cash equivalents, end of period	171,894	205,818
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	1,661	1,827
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid	6,578	7,691
Vesting of early exercised stock options	$ 546	$ 486